Polishing composition, method for producing polishing composition and polishing composition preparation kit

ABSTRACT

Provided are polishing compositions comprising a water-soluble polymer and water. The water-soluble polymer of an embodiment has a repeat unit that does not have any hydroxyl groups, and the water-soluble polymer has a hydroxyl group content in a range of 4 mmol/g or higher and 21 mmol/g or lower. The water-soluble polymer of another embodiment has a repeat unit A that has a hydroxyl group and a repeat unit B, and the number of moles of the repeat unit B in the total number of moles of all the repeat units of the water-soluble polymer is 5% or greater.

CROSS-REFERENCE

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 14/777,841, filed on Sep. 17, 2015, and now issuedas U.S. Pat. No. 10,351,732, which is a U.S. national phase ofInternational Application No. PCT/JP2014/057008, filed on Mar. 14, 2014,which claims priority to Japanese Patent Application Publication Nos.2013-057225, 2013-057226, 2013-057227 and 2013-057228 filed on Mar. 19,2013, and the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a polishing composition used forpolishing a polishing object. In particular, it relates to a polishingcomposition used primarily for polishing semiconductor substrates suchas silicon wafers and the like as well as other substrates.

The present invention relates also to a method for producing a polishingcomposition used for polishing a polishing object and further relates toa polishing composition preparation kit used in the production method.

2. Description of the Related Art

The surface of a silicon wafer used as a component of a semiconductordevice, etc., is generally polished to a high quality mirror finish viaa lapping step (rough polishing step) and a polishing step (precisionpolishing step). The polishing step typically comprises a firstpolishing step and a final polishing step. Japanese Patent No. 4772156is cited as a technical literature related to polishing compositionsused primarily for polishing semiconductor substrates such as siliconwafers, etc. WO 2010/143579 is a technical literature related to apolishing composition used primarily for polishing an insulating filmsuch as a silicon oxide film, etc.

SUMMARY OF THE INVENTION

Polishing compositions (especially polishing compositions for precisionpolishing) for polishing semiconductor substrates such as silicon wafersas well as other substrates are expected to have abilities to producesurfaces with low haze and a fewer number of micro particles (lightpoint defect or LPD) after polishing. Many of polishing compositions forsuch purposes comprise, besides water and an abrasive, a water-solublepolymer for protecting the surface of a polishing object (an article tobe polished, or work piece) or increasing the wettability, etc. of thesame. Among them, hydroxyethyl cellulose is cited as a widely used,water-soluble polymer.

However, since hydroxyethyl cellulose (HEC) is a polymer derived from anatural compound (cellulose), there are limitations in managing thechemical structure and purity as compared with a polymer obtainable byartificial polymerization of monomers (i.e. a synthetic polymer). Forinstance, commercially readily available HECs are limited in weightaverage molecular weight and range of molecular weight distribution(ratio of weight average molecular weight (Mw) to number averagemolecular weight (Mn), i.e. Mw/Mn). In addition, since they are derivedfrom natural compounds, it is difficult to significantly reduceimpurities and local disorder (microscale aggregation, etc.) in theirpolymer structures, etc., that may cause surface defect. The amounts andextent of such impurities, etc., are likely to vary widely as well. Asmore strict requirements are expected for surface quality in the future,it will be useful to provide a polishing composition excellent inreducing the number of LPD and haze, with the composition notessentially requiring an HEC.

In view of such circumstances, an objective of the present invention isto provide a polishing composition excellent in reducing the number ofLPD and haze. Another related objective is to provide a method forproducing a polished article, using such a polishing composition.

A typical polishing composition for polishing semiconductor substratessuch as silicon wafers and other substrates comprises an abrasive,water, and a water-soluble polymer; and further comprises a basiccompound to adjust the pH to a basic pH. It is preferable to adjust thepolishing composition to a basic pH from the standpoint of stabilizingthe dispersion of the abrasive and increasing the polishing rate.

Some water-soluble polymers, however, undergo hydrolysis under basicconditions. When a water-soluble polymer in a polishing composition ishydrolyzed, the polishing composition may suffer performancedeterioration over time. Thus, in a polishing composition adjusted to abasic pH (or a “basic polishing composition” hereinafter), the use of awater-soluble polymer that is hydrolytic under basic conditions(alkaline-hydrolytic water-soluble polymer) has been avoided toinconveniently limit the choice of compositions.

In a basic polishing composition, it will be useful to improve theperformance stability while using an alkaline-hydrolytic water-solublepolymer. Thus, another objective of the present invention is to providea technique that uses a water-soluble polymer having analkaline-hydrolytic functional group to produce a basic polishingcomposition with greater performance stability

Solution to Problem

The polishing composition according to a first aspect provided by thisspecification comprises a water-soluble polymer having a molecularstructure including a plurality of repeat unit species with differenttypes of unit species. In the water-soluble polymer, the plurality ofrepeat unit species comprise a repeat unit A and a repeat unit B whichis different from the repeat unit A.

When used for polishing a polishing object, the polishing compositiondisclosed herein typically comprises an abrasive in addition to thewater-soluble polymer. According to the polishing composition in such anembodiment, the mechanical work of the abrasive can increase thepolishing efficiency.

As the water-soluble polymer, a nonionic polymer can be preferably used.According to the polishing composition comprising a nonionicwater-soluble polymer, it is possible to bring about greater effect toreduce the haze and the number of LPD in the polished surface.

A preferable example of the water-soluble polymer comprises a vinylalcohol unit as the repeat unit A. Herein, the vinyl alcohol unit refersto the structural moiety corresponding to the structure formed bypolymerization of the vinyl group of vinyl alcohol (CH₂═CH—OH). Inparticular, the vinyl alcohol unit is the structural moiety representedby the chemical formula —CH₂—CH(OH)—. A polishing composition comprisingsuch a water-soluble polymer can bring about greater effect to reducethe haze and the number of LPD in the polished surface.

Another preferable example of the water-soluble polymer comprises avinyl acetate unit as the repeat unit B. Herein, the vinyl acetate unitrefers to the structural moiety corresponding to the structure formed bypolymerization of the vinyl group of vinyl acetate (CH₃COOCH═CH₂). Thevinyl acetate unit is the structural moiety represented by the chemicalformula —CH₂—CH(OCOCH₃)—. A polishing composition comprising such awater-soluble polymer can bring about greater effect to reduce the hazeand the number of LPD in the polished surface.

When the water-soluble polymer comprises a vinyl acetate unit, the molarratio (ratio of the number of moles) of the vinyl acetate unit to thetotal number of moles of all the repeat units in the molecular structureof the water-soluble polymer is preferably in a range between 5% and80%. A polishing composition comprising such a water-soluble polymer canbring about greater effect to reduce the haze and the number of LPD inthe polished surface.

The polishing composition disclosed herein can be preferably made in anembodiment further comprising a basic compound. A polishing compositionin such an embodiment can increase the polishing efficiency by theeffect of the basic compound.

This specification also provides a method for producing a polishedarticle, using a polishing composition disclosed herein. The methodcomprises supplying a polishing liquid (the term “liquid” hereinencompasses a slurry) to a polishing object (work piece). It furthercomprises polishing a surface of the polishing object with the polishingliquid. According to such a production method, a polished articlecomprising a high-quality surface (e.g. with fewer LPD and low haze) canbe produced.

The art disclosed herein can be preferably applied to polishing asilicon wafer, for instance, a lapped silicon wafer. An example ofparticularly preferable applications is final polishing of a siliconwafer.

The polishing composition according to a second aspect provided by thisspecification comprises an abrasive, a water-soluble polymer and water.The polishing composition is characterized by exhibiting an etching rateof 2.0 nm/min or lower based on the following etching rate measurement:

[Etching Rate Measurement]

(1A) An etching rate measuring reagent LE is prepared, comprising 0.18%by mass of the water-soluble polymer and 1.3% by mass of ammonia withthe rest being water.

(2A) A silicon substrate (in a 6 cm long by 3 cm wide by 775 μm thickrectangle) is obtained, from which surface natural oxide film isremoved, and its mass W0 is measured.

(3A) The silicon substrate is immersed in the reagent LE at roomtemperature for 12 hours.

(4A) The silicon substrate is removed from the reagent LE and cleaned atroom temperature for 10 seconds with a cleaning solution formed of NH₃(29%)/H₂O₂(31%)/ultrapure water=1/1/8 (volume ratio).

(5A) The cleaned silicon substrate is measured for its mass W1.

(6A) From the difference between the W0 and W1 as well as the specificgravity of the silicon substrate, the etching rate (nm/min) isdetermined.

In addition, the polishing composition is characterized by having anabrasive adsorption of 20% or lower based on the following abrasiveadsorption measurement.

[Abrasive Adsorption Measurement]

(1B) The polishing composition is centrifuged to precipitate theabrasive and the resulting supernatant is subjected to measurement oftotal organic carbon to determine the total amount of organic carbon,C1, in the supernatant.

(2B) A test solution L0 is obtained, having the same composition as thatof the polishing composition but without the abrasive; and the testsolution L0 is subjected to measurement of total organic carbon todetermine the total amount of organic carbon, C0, in the test solutionL0.

(3B) From the C0 and C1, the abrasive adsorption is determined by thefollowing equation:Abrasive adsorption (%)=[(C0−C1)/C0]×100

A polishing composition that satisfies the etching rate and abrasiveadsorption can reduce the haze and the number of LPD in the polishedsurface when compared with a polishing composition that does not satisfythe etching rate and/or the abrasive adsorption. For instance, the hazeand the number of LPD in the polished surface can be reduced incomparison to a polishing composition using hydroxyethyl cellulose asthe water-soluble polymer (i.e., the polishing composition typicallyhaving an abrasive adsorption of greater than 20%).

As the water-soluble polymer, a nonionic polymer can be preferably used.This may bring about greater effect to reduce the haze and the number ofLPD in the polished surface.

A preferable example of the water-soluble polymer has a molecularstructure comprising a vinyl alcohol unit and a vinyl acetate unit asthe repeat units. Herein, the vinyl alcohol unit refers to thestructural moiety corresponding to the structure formed bypolymerization of the vinyl group of vinyl alcohol (CH₂═CH—OH). Inparticular, the vinyl alcohol unit is the structural moiety representedby the chemical formula —CH₂—CH(OH)—. The vinyl acetate unit refers tothe structural moiety corresponding to the structure formed bypolymerization of the vinyl group in vinyl acetate (CH₃COOCH═CH₂). Thevinyl acetate unit is the structural moiety represented by the chemicalformula —CH₂—CH(OCOCH₃)—. A polishing composition comprising such awater-soluble polymer can bring about greater effect to reduce the hazeand the number of LPD in the polished surface.

When the water-soluble polymer comprises a vinyl acetate unit, the molarratio (ratio of the number of moles) of the vinyl acetate unit to thetotal number of moles of all the repeat units in the molecular structureof the water-soluble polymer is preferably in a range between 5% and80%. A polishing composition comprising such a water-soluble polymer canbring about greater effect to reduce the haze and the number of LPD inthe polished surface.

The polishing composition disclosed herein can be preferably made in anembodiment further comprising a basic compound in addition to theabrasive, water-soluble polymer and water. A polishing composition insuch an embodiment can increase the polishing efficiency by the effectof the basic compound.

This specification also provides a method for producing a polishedarticle, using a polishing composition disclosed herein. The methodcomprises supplying a polishing liquid (the term “liquid” hereinencompasses a slurry) to a polishing object (work piece). It furthercomprises polishing a surface of the polishing object with the polishingliquid. According to such a production method, a polished articlecomprising a high-quality surface (e.g. with fewer LPD and low haze) canbe produced.

The art disclosed herein can be preferably applied to polishing asilicon wafer, for instance, polishing a lapped silicon wafer. Anexample of particularly preferable applications is final polishing of asilicon wafer.

The polishing composition according to a third aspect provided by thisspecification comprises a water-soluble polymer and water. Thewater-soluble polymer has a repeat unit that does not have any hydroxylgroups, and the water-soluble polymer has a hydroxyl group content in arange of 4 mmol/g or higher and 21 mmol/g or lower. A polishingcomposition comprising such a water-soluble polymer may have a greaterability to reduce the haze and the number of LPD in a polished surfacewhen compared with, for instance, a polishing composition in which thewater-soluble polymer is replaced with the same amount of hydroxyethylcellulose.

The polishing composition according to the third aspect can be relatedto the polishing composition according to the first aspect describedabove. Typically, part or all of the polishing composition according tothe third aspect can be included in the polishing composition accordingto the first aspect. Also, the polishing composition according to thethird aspect may be related to the polishing composition according tothe second aspect described above, and may be a combination ormodification of part or all of the polishing composition according tothe first aspect and part or all of the polishing composition accordingto the second aspect.

In a preferable embodiment, the water-soluble polymer is nonionic. Also,the water-soluble polymer typically has a repeat unit A that has ahydroxyl group. The water-soluble polymer preferably has a vinyl alcoholunit as the repeat unit A. Such a water-soluble polymer may have aweight average molecular weight of 1×10⁴ or higher.

In a preferable embodiment, the repeat unit that does not have anyhydroxyl groups is at least one selected from the group consisting of apropylene oxide unit, an ethylene oxide unit, an N-isopropylacrylamideunit and a vinyl hexanoate unit.

The polishing composition according to a fourth aspect provided by thisspecification comprises a water-soluble polymer and water. Thewater-soluble polymer has a repeat unit A that has a hydroxyl group anda repeat unit B. The number of moles of the repeat unit B in the totalnumber of moles of all the repeat units of the water-soluble polymer is5% or greater. The number of moles of the repeat unit B in the totalnumber of moles of all the repeat units of the water-soluble polymer ispreferably 10% or greater. The polishing composition according to thefourth aspect can be related to the polishing composition according tothe first aspect described above. Typically, part or all of thepolishing composition according to the fourth aspect can be included inthe polishing composition according to the first aspect. Also, thepolishing composition according to the fourth aspect may be related tothe polishing composition according to the second aspect describedabove, and may be a combination or modification of part or all of thepolishing composition according to the first aspect and part or all ofthe polishing composition according to the second aspect.

In a preferable embodiment, the water-soluble polymer is nonionic. Thewater-soluble polymer preferably has a hydroxyl group content in a rangeof 4 mmol/g or higher and 21 mmol/g or lower. The repeat unit Apreferably comprises a vinyl alcohol unit. Such a water-soluble polymermay have a weight average molecular weight of 1×10⁴ or higher.

In a preferable embodiment, the repeat unit B is at least one selectedfrom the group consisting of a vinyl acetate unit, an acryloylmorpholineunit and an N-vinylpyrrolidone unit.

The polishing composition production method according to the firstaspect provided by this specification is a method for producing apolishing composition, using an abrasive, a basic compound and awater-soluble polymer H having an alkaline-hydrolytic functional group,and water. The method comprising a step of obtaining an agent A thatcomprises at least the basic compound and a step of obtaining an agent Bthat comprises at least the water-soluble polymer H. The productionmethod further comprises a step of mixing a first composition comprisingat least the agent A and a second composition comprising at least theagent B to prepare a mixture that comprises the abrasive, the basiccompound, the water-soluble polymer H and water at a concentration ofthe basic compound of 0.1 mol/L or lower. According to such a productionmethod, a polishing composition can be produced, having greaterperformance stability.

The production method can be preferably implemented in an embodimentwherein the abrasive is included at least in the agent A, or in otherwords, in an embodiment wherein the agent A comprises the basiccompound, the abrasive and water. Such an embodiment using an agent Acomprising an abrasive and a basic compound is preferable from thestandpoint of the dispersion stability of the abrasive. The productionmethod may be implemented in an embodiment wherein the abrasive isincluded at least in the agent B, or in other words, in an embodimentwherein the agent B comprises the water-soluble polymer H, the abrasiveand water. Both of the agent A and the agent B may comprise theabrasive.

In a preferable embodiment of the production method disclosed herein,the agent A is an abrasive dispersion C comprising the abrasive, thebasic compound and water. The abrasive dispersion C is diluted toprepare the first composition; and then, the first composition is mixedwith the second composition to prepare the mixture. According to such anembodiment, a polishing composition with good dispersion of the abrasiveand excellent performance stability can be produced.

This specification also provides another method for producing apolishing composition, using an abrasive, a basic compound, awater-soluble polymer H having an alkaline-hydrolytic functional group,and water. The method comprises a step of obtaining an agent Acomprising at least the basic compound and a step of obtaining an agentB comprising at least the water-soluble polymer H. The production methodfurther comprises a step of mixing a first composition comprising atleast the agent A and a second composition comprising at least the agentB to prepare a mixture that comprises the abrasive, the basic compound,the water-soluble polymer H and water at a concentration of the abrasiveof lower than 3% by mass. According to such a production method, apolishing composition can be produced with greater performancestability.

The production method can be preferably implemented in an embodimentwherein the abrasive is included at least in the agent A, or in otherwords, in an embodiment wherein the agent A comprises the basiccompound, the abrasive and water. Such an embodiment using an agent Acomprising an abrasive and a basic compound is preferable from thestandpoint of the dispersion stability of the abrasive. The productionmethod may be implemented in an embodiment wherein the abrasive isincluded at least in the agent B, or in other words, in an embodimentwherein the agent B comprises the water-soluble polymer H, the abrasiveand water. Each of the agent A and the agent B may comprise theabrasive.

In a preferable embodiment of the production method disclosed herein,the agent A is an abrasive dispersion C comprising the abrasive, thebasic compound and water. The abrasive dispersion C is diluted toprepare the first composition; and then, the first composition is mixedwith the second composition to prepare the mixture. According to such anembodiment, a polishing composition with good dispersion of the abrasiveand excellent performance stability can be produced.

From the standpoint of the dispersibility of the abrasive and theperformance stability of the polishing composition, the abrasivedispersion C can be diluted in such a manner that water is added to theabrasive dispersion C to form the first composition at a concentrationof the abrasive below 3% by mass. Prior to the dilution, the abrasivedispersion C preferably has an abrasive concentration of, for instance,3% by mass or higher. This may lead to reduction of costs related to thestorage and transport of the abrasive dispersion C.

This specification also provides another method for producing apolishing composition, using an abrasive, a basic compound, awater-soluble polymer H having an alkaline-hydrolytic functional group,and water. This production method is characterized by allowing theabrasive and the water-soluble polymer H to be co-present in watercontaining less than 3% by mass of the abrasive simultaneously with orbefore allowing the co-presence of the basic compound and thewater-soluble polymer H. According to such a method, a polishingcomposition can be produced with greater performance stability.

The art disclosed herein can be preferably applied to production of, forinstance, a polishing composition that uses a water-soluble polymer Hhaving an acyloxy group (e.g. acetoxy group) as the alkaline-hydrolyticfunctional group. It is particularly meaningful to produce a polishingcomposition comprising such a water-soluble polymer H by applying themethod disclosed herein because its properties, and consequently itspolishing abilities, are likely to be altered by hydrolysis of theacyloxy group.

The art disclosed herein can be preferably applied to production of apolishing composition that uses a water-soluble polymer H comprising avinyl acetate unit and a vinyl alcohol unit as repeat units in themolecular structure. Herein, the vinyl alcohol unit refers to thestructural moiety corresponding to the structure formed bypolymerization of the vinyl group in vinyl alcohol (CH₂═CH—OH). Inparticular, the vinyl alcohol unit is the structural moiety representedby the chemical formula —CH₂—CH(OH)—. The vinyl acetate unit refers tothe structural moiety corresponding to the structure formed bypolymerization of the vinyl group in vinyl acetate (CH₃COOCH═CH₂). Thevinyl acetate unit is the structural moiety represented by the chemicalformula —CH₂—CH(OCOCH₃)—, and is a repeat unit having an acetoxy groupas the alkaline-hydrolytic functional group. It is particularlymeaningful to produce a polishing composition comprising such awater-soluble polymer H by applying the method disclosed herein becauseits properties (polishing abilities) are likely altered by hydrolysis ofthe acyloxy group.

As the water-soluble polymer H, a nonionic polymer can be preferablyused. A polishing composition produced with such a water-soluble polymerH may be of higher performance (e.g. capable of producing greater effectto reduce the haze value and/or the number of LPD in the polishedsurface).

This specification also provides a polishing composition preparation kitpreferably used in a polishing composition production method disclosedherein. The kit comprises the agent A and the agent B that are storedseparately. With the use of a kit in such a form, the polishingcomposition production method disclosed herein can be easilyimplemented.

In such a polishing composition preparation kit, the agent A comprisesat least the basic compound and the agent B comprises at least thewater-soluble polymer H. The abrasive may be included in either theagent A or agent B, or in each of the agent A and agent B. The polishingcomposition preparation kit may be in such a form that the abrasive isstored as an agent C other than as the agent A or the agent B.

Alternatively, the polishing composition preparation kit may be free ofthe abrasive. The polishing composition preparation kit in such a formcan be preferably applied to the polishing composition production methoddisclosed herein, for instance, by combining the kit with an abrasiveobtained separately from the kit.

This specification also provides a method for producing a polishedarticle, using a polishing composition produced by a method disclosedherein. The method comprises supplying a polishing liquid (the term“liquid” herein encompasses a slurry) comprising the polishingcomposition to a polishing object. It further comprises polishing asurface of the polishing object with the polishing liquid. According tosuch a production method, a polished article comprising a high-qualitysurface (e.g. with fewer LPD and low haze) can be produced.

The art disclosed herein can be preferably applied to production of apolishing composition used for polishing a silicon wafer, for instance,for polishing a lapped silicon wafer. An example of a particularlypreferable application (product) is a polishing composition for use infinal polishing of a silicon wafer.

The polishing composition production method according to the secondaspect provided by this specification is a method for producing apolishing composition, using an abrasive, a basic compound and awater-soluble polymer H having an alkaline-hydrolytic functional group,and water; the method comprising a step of obtaining an agent A thatcomprises at least the basic compound and a step of obtaining an agent Bthat comprises at least the water-soluble polymer H. The productionmethod further comprises a step of mixing at least the agent A and theagent B to prepare a polishing composition stock solution having aconcentration of the basic compound of higher than 0.02 mol/L and a stepof diluting the polishing composition stock solution to a concentrationof the basic composition of 0.02 mol/L or lower within 24 hours afterthe agent A and the agent B are mixed. According to such a method, apolishing composition can be produced with improved performancestability.

The production method can be preferably implemented in an embodimentwherein the abrasive is included at least in the agent A, or in otherwords, in an embodiment wherein the agent A comprises the basiccompound, the abrasive and water. Such an embodiment using an agent Acomprising an abrasive and a basic compound is preferable from thestandpoint of the dispersion stability of the abrasive. The productionmethod may be implemented in an embodiment wherein the abrasive isincluded at least in the agent B, or in other words, in an embodimentwherein the agent B comprises the water-soluble polymer H, the abrasiveand water. Each of the agent A and the agent B may comprise theabrasive.

This specification also provides another method for producing apolishing composition, using an abrasive, a basic compound, awater-soluble polymer H having an alkaline-hydrolytic functional group,and water. The method comprises a step of obtaining an agent Acomprising at least the basic compound and a step of obtaining an agentB comprising at least the water-soluble polymer H. The production methodfurther comprises a step of mixing at least the agent A and the agent Bto prepare a polishing composition stock solution having a 1% by mass orhigher abrasive content and a step of diluting the polishing compositionstock solution to an abrasive content of less than 1% by mass within 24hours after the agent A and the agent B are mixed. According to such amethod, a polishing composition can be produced with improvedperformance stability.

The production method can be preferably implemented in an embodimentwherein the abrasive is included at least in the agent A, or in otherwords, in an embodiment wherein the agent A comprises the basiccompound, the abrasive and water. Such an embodiment using an agent Acomprising an abrasive and a basic compound is preferable from thestandpoint of the dispersion stability of the abrasive. The productionmethod may be implemented in an embodiment wherein the abrasive isincluded at least in the agent B, or in other words, in an embodimentwherein the agent B comprises the water-soluble polymer H, the abrasiveand water. Each of the agent A and the agent B may comprise theabrasive.

A production method disclosed herein can be preferably implemented in anembodiment wherein the stock solution is diluted by a factor of 10 orgreater by volume in the step of diluting the polishing compositionstock solution. According to such an embodiment, at least either theagent A or the agent B used in preparing the stock solution can have arelatively high concentration. This is advantageous from the standpointof the convenience and costs of production, distribution, storage, etc.,of the materials used for preparation of the stock solution.

The art disclosed herein may be preferably applied to production of, forinstance, a polishing composition using a water-soluble polymer havingan acyloxy group (e.g. acetoxy group) as the alkaline-hydrolyticfunctional group. It is particularly meaningful to produce a polishingcomposition comprising such a water-soluble polymer H by applying themethod disclosed herein because its properties, and consequently itspolishing abilities, are likely to be altered by hydrolysis of theacyloxy group.

The art disclosed herein can be preferably applied to production of apolishing composition that uses a water-soluble polymer H comprisingvinyl acetate units at a molar ratio of 5% or higher relative to all therepeat units in the molecular structure. The vinyl acetate unit refersto the structural moiety corresponding to the structure formed bypolymerization of the vinyl group in vinyl acetate (CH₃COOCH═CH₂). Thevinyl acetate unit is the structural moiety represented by the chemicalformula —CH₂—CH(OCOCH₃)—, and is a repeat unit having an acetoxy groupas the alkaline-hydrolytic functional group. It is particularlymeaningful to produce a polishing composition comprising such awater-soluble polymer H by applying the method disclosed herein becauseits properties, and consequently its polishing abilities, are likely tobe altered by hydrolysis of the acyloxy group.

The art disclosed herein can be preferably applied to production of apolishing composition that uses a water-soluble polymer H having amolecular structure that comprises a vinyl acetate unit and a vinylalcohol unit as repeat units. Herein, the vinyl alcohol unit refers tothe structural moiety corresponding to the structure formed bypolymerization of the vinyl group of vinyl alcohol (CH₂═CH—OH). Inparticular, the vinyl alcohol unit is the structural moiety representedby the chemical formula —CH₂—CH(OH)—. The vinyl acetate unit is asdescribed earlier. It is particularly meaningful to produce a polishingcomposition comprising such a water-soluble polymer H by applying themethod disclosed herein because its properties, and consequently itspolishing abilities, are likely to be altered by hydrolysis of theacyloxy group.

As the water-soluble polymer H, a nonionic polymer can be preferablyused. A polishing composition produced with such a water-soluble polymerH may be of higher performance (e.g. capable of producing greater effectto reduce the haze value and/or the number of LPD in the polishedsurface).

This specification also provides a polishing composition preparation kitpreferably used in a polishing composition production method disclosedherein. The kit comprises the agent A and the agent B that are storedseparately. With the use of a kit in such a form, the polishingcomposition production method disclosed herein can be easilyimplemented.

In such a polishing composition preparation kit, the agent A comprisesat least the basic compound and the agent B comprises at least thewater-soluble polymer H. The abrasive may be included in either theagent A or agent B, or in each of the agent A and agent B. The polishingcomposition preparation kit may be in such a form that the abrasive isstored as an agent C other than as the agent A or the agent B.

Alternatively, the polishing composition preparation kit may be free ofthe abrasive. The polishing composition preparation kit in such a formcan be preferably applied to the polishing composition production methoddisclosed herein, for instance, by combining the kit with an abrasiveobtained separately from the kit.

This specification also provides a method for producing a polishedarticle, using a polishing composition produced by a method disclosedherein. The method comprises supplying a polishing liquid (the term“liquid” herein encompasses a slurry) comprising the polishingcomposition to a polishing object. It further comprises polishing asurface of the polishing object with the polishing liquid. According tosuch a production method, a polished article comprising a high-qualitysurface (e.g. with fewer LPD and low haze) can be produced.

The art disclosed herein can be preferably applied to production of apolishing composition used for polishing a silicon wafer, for instance,for polishing a lapped silicon wafer. An example of a particularlypreferable application (product) is a polishing composition for use infinal polishing of a silicon wafer.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are described below.Matters necessary to implement this invention other than thosespecifically referred to in this specification may be understood asdesign matters to a person of ordinary skill in the art based on theconventional art in the pertinent field. The present invention can beimplemented based on the contents disclosed in this specification andcommon technical knowledge in the subject field. In the presentspecification, the terms “weight,” “% by weight” and “parts by weight”are used synonymously to “mass,” “% by mass” and “parts by mass,”respectively.

<<1. Polishing Composition According to First Aspect>>

The polishing composition according to the first aspect disclosed hereinis characterized by comprising a water-soluble polymer that satisfiesthe following conditions:

the water-soluble polymer has a molecular structure comprising aplurality of repeat unit species with different types of unit species;and

the plurality of repeat unit species comprises a repeat unit A and arepeat unit B which is different from the repeat unit A.

In an embodiment (third aspect), the polishing composition comprises awater-soluble polymer and water. The water-soluble polymer in thisembodiment is characterized by having a repeat unit that does not haveany hydroxyl groups, and having a hydroxyl group content in a range of 4mmol/g or higher and 21 mmol/g or lower.

In an embodiment (fourth aspect), the polishing composition comprises awater-soluble polymer and water. The water-soluble polymer in thisembodiment is characterized by having a repeat unit A that has ahydroxyl group and a repeat unit B, and the number of moles of therepeat unit B in the total number of moles of all the repeat units being5% or greater.

The polishing composition according to the first aspect is described indetail below.

<1-1. Water-Soluble Polymer>

The polishing composition in a preferable embodiment (first aspect) maycomprise a water-soluble polymer having a repeat unit A and a repeatunit B. The repeat unit B is referred to as a unit different from therepeat unit A.

The water-soluble polymer may comprise one species of repeat unit A, ortwo or more such species in combination. Specific examples of the repeatunit A include those shown in Table 1 below.

TABLE 1 Repeat unit Structure Acrylamide —CH₂—CH(CONH₂)— Vinyl alcohol—CH₂—CH(OH)— Acrylic acid —CH₂—CH(COOH)—

The water-soluble polymer may comprise one species of repeat unit B, ortwo or more such species in combination. Specific examples of the repeatunit B include those shown in Table 2 below.

TABLE 2 Repeat unit Structure Propylene oxide —CH₂—CH(CH₃)—O— Ethyleneoxide —CH₂—CH₂—O— N-isopropylacrylamide

Acryloylmorpholine

N-vinylpyrrolidone

Vinyl acetate —CH₂—CH(OCOCH₃)— Vinyl hexanoate —CH₂—CH(OCOC₅H₁₁)—

In the water-soluble polymer disclosed herein, the number of moles ofthe repeat unit A in the total number of moles of all the repeat unitsis typically 95% or less, preferably 90% or less, more preferably 85% orless, or 80% or less for instance. In such a water-soluble polymer, thenumber of moles of the repeat unit A in the total number of moles of allthe repeat units is typically 20% or greater, preferably 40% or greater,more preferably 50% or greater, or yet more preferably 60% or greater,or 70% or greater for instance.

In the water-soluble polymer disclosed herein, the number of moles ofthe repeat unit B in the total number of moles of all the repeat unitsis typically 5% or greater, preferably 10% or greater, more preferably15% or greater, or 20% or greater for instance. In such a water-solublepolymer, the number of moles of the repeat unit B in the total number ofmoles of all the repeat units is typically 80% or less, preferably 60%or less, more preferably 50% or less, or yet more preferably 40% orless, or 30% or less for instance.

A preferable example of the water-soluble polymer comprises a hydroxylgroup-containing repeat unit as the repeat unit A. Such a water-solublepolymer is preferable since it is likely to show excellent watersolubility. The water-soluble polymer comprising a hydroxylgroup-containing repeat unit as the repeat unit A typically has ahydroxyl group content of 4 mmol/g or higher, preferably 8 mmol/g orhigher, more preferably 12 mmol/g or higher, or may be 16 mmol/g orhigher (for instance 20 mmol/g or higher). Such a water-soluble polymertypically has a hydroxyl group content of 21 mmol/g or lower, preferably20 mmol/g or lower, more preferably 19 mmol/g or lower, or may be 17mmol/g or lower (for instance, 15 mmol/g or lower). A typical example ofthe hydroxyl group-containing repeat unit A is vinyl alcohol unit.

A preferable example of the water-soluble polymer comprises a vinylmonocarboxylate unit as the repeat unit B. Preferable specific examplesof the vinyl monocarboxylate unit include vinyl acetate unit, vinylhexanoate unit, and the like.

In a preferable embodiment, as the repeat unit B constituting awater-soluble polymer, one or two or more of a propylene oxide unit, anethylene oxide unit, an N-isopropylacrylamide unit, a vinyl hexanoateunit. and a butyl vinyl ether unit can be used.

In a preferable embodiment, as the repeat unit B constituting awater-soluble polymer, one or two or more of a vinyl acetate unit, anacryloylmorpholine unit and an N-vinylpyrrolidone unit can be used.

A preferable example of the vinyl monocarboxylate unit-containingwater-soluble polymer comprises a vinyl acetate unit as the repeat unitB. In such a water-soluble polymer, the number of moles of vinyl acetateunits in the total number of moles of all the repeat units is typically5% or greater, more preferably 10% or greater, yet more preferably 15%or greater, or particularly preferably 20% or greater. The number ofmoles of vinyl acetate units in the total number of moles of all therepeat units is not particularly limited. From the standpoint of thewater solubility, etc., it is usually suitably 80% or less, preferably60% or less, more preferably 50% or less, or yet more preferably 40% orless.

Another preferable example of the vinyl monocarboxylate unit-containingwater-soluble polymer comprises a vinyl hexanoate unit as the repeatunit B. The number of moles of vinyl hexanoate units in the total numberof moles of all the repeat units is typically, but not particularlylimited to, 5% or greater, more preferably 10% or greater, or yet morepreferably 15% or greater. From the standpoint of the water solubility,etc., the number of moles of vinyl hexanoate units in the total numberof moles of all the repeat units is usually, but not particularlylimited to, 80% or less, preferably 60% or less, more preferably 50% orless, or yet more preferably 40% or less (e.g. 30% or less).

The art disclosed herein can be preferably implemented in an embodimentusing a water-soluble polymer that comprises a vinyl alcohol unit as therepeat unit A and a vinyl acetate unit as the repeat unit B. An exampleof such a water-soluble polymer has a structure resulting from partialsaponification of vinyl acetate homopolymer or copolymer. For instance,a partially-saponified polyvinyl alcohol having a structure resultingfrom partial saponification of vinyl acetate homopolymer can bepreferably used. The partially-saponified polyvinyl alcohol is awater-soluble polymer formed of vinyl alcohol units and vinyl acetateunits.

The art disclosed herein can be preferably implemented in an embodimentusing a water-soluble polymer that comprises a vinyl alcohol unit as therepeat unit A and a vinyl hexanoate unit as the repeat unit B. Anexample of such a water-soluble polymer has a structure resulting frompartial saponification of vinyl hexanoate homopolymer or copolymer. Forinstance, a partially-saponified polyvinyl alcohol resulting frompartial saponification of a copolymer of vinyl acetate and vinylhexanoate can be preferably used. Examples of the partially-saponifiedpolyvinyl alcohol include a water-soluble polymer formed of vinylalcohol units and vinyl hexanoate units as well as a water-solublepolymer formed of vinyl alcohol units, vinyl acetate units and vinylhexanoate units.

From the standpoint of the water solubility, etc., as thepartially-saponified polyvinyl alcohol, a species having a degree ofsaponification of 50% by mole or higher (more preferably 60% by mole orhigher) can be preferably used.

The water-soluble polymer is preferably nonionic. In other words, awater-soluble polymer essentially free of anionic and cationic repeatunits is preferable. Herein, being essentially free of anionic andcationic repeat units means that the molar ratio of these repeat unitsis lower than 0.02% (e.g. lower than 0.001%). According to the polishingcomposition that comprises a nonionic water-soluble polymer, it ispossible to obtain greater effect to reduce the haze and the number ofLPD in the polished surface. The water-soluble polymer being nonionic ispreferable also from the standpoint of reducing aggregates andincreasing the washability, etc.

The molecular weight of the water-soluble polymer is not particularlylimited. For instance, a water-soluble polymer having a weight averagemolecular weight (Mw) of 200×10⁴ or smaller (typically 1×10⁴ to 200×10⁴,e.g. 1×10⁴ to 150×10⁴) can be used. From the standpoint of preventingformation of aggregates to a greater extent, the use of a water-solublepolymer having a Mw of smaller than 100×10⁴ (more preferably 80×10⁴ orsmaller, yet more preferably 50×10⁴ or smaller, typically 40×10⁴ orsmaller, e.g. 30×10⁴ or smaller) is preferable. From the standpoint ofthe ease of filtering and washing the polishing composition, etc., awater-soluble polymer having a Mw of 25×10⁴ or smaller (more preferably20×10⁴ or smaller, yet more preferably 15×10⁴ or smaller, typically10×10⁴ or smaller, e.g. 5×10⁴ or smaller) can be preferably used. On theother hand, in general, with increasing Mw of water-soluble polymer, thehaze reduction effect tends to increase. From such a standpoint, it isusually preferable to use a water-soluble polymer having a Mw of 0.1×10⁴or larger (typically 0.2×10⁴ or larger, e.g. 1×10⁴ or larger).

In the polishing composition according to the first aspect disclosedherein, a water-soluble polymer having a Mw of 3×10⁴ or smaller can bepreferably used. The Mw of the water-soluble polymer can be 2×10⁴ orsmaller, 1×10⁴ or smaller, or even smaller than 0.5×10⁴ (e.g. smallerthan 0.4×10⁴). The Mw of the water-soluble polymer is typically 0.1×10⁴or larger, or usually preferably 0.2×10⁴ or larger. The Mw range can bepreferably applied to, for instance, a water-soluble polymer comprisinga vinyl alcohol unit as the repeat unit A (e.g. a partially-saponifiedpolyvinyl alcohol).

The relationship between the weight average molecular weight (Mw) andnumber average molecular weight (Mn) of the water-soluble polymer is notparticularly limited. From the standpoint of preventing the formation ofaggregates, etc., a water-soluble polymer having a molecular weightdistribution (Mw/Mn) of 5.0 or less can be preferably used. From thestandpoint of the performance stability of the polishing composition,etc., the water-soluble polymer has an Mw/Mn of preferably 4.0 or less,more preferably 3.5 or less, or yet more preferably 3.0 or less (e.g.2.5 or less). Theoretically, the Mw/Mn is 1.0 or greater. From thestandpoint of the availability of starting materials and the ease ofsynthesis, in usual, a water-soluble polymer having an Mw/Mn of 1.05 orgreater can be preferably used.

As the Mw and Mn of a water-soluble polymer, the values based on aqueousgel permeation chromatography (GPC) (aqueous, based on standardpolyethylene oxide) can be used.

<1-2. Water>

The polishing composition disclosed herein typically comprises water inaddition to the water-soluble polymer. As the water in the polishingcomposition disclosed herein, ion-exchanged water (deionized water),pure water, ultrapure water, distilled water and the like can bepreferably used. To avoid hindering the effects of other components inthe polishing composition whenever possible, in the water used, forinstance, the total transition metal ion content is preferably 100 ppbor less. For example, the purity of the water can be increased byoperations such as removing impurity ions with ion-exchange resin,removing contaminants with a filter, distillation, and so on.

The polishing composition disclosed herein may further comprise, asnecessary, a water-miscible organic solvent (lower alcohol, lowerketone, etc.). In usual, of the solvent in the polishing composition,preferably 90% by volume or more is water, or more preferably 95% byvolume or more (typically 99 to 100% by volume) is water.

The polishing composition disclosed herein (typically a slurrycomposition) can be preferably implemented, for instance, in anembodiment in which the non-volatile content (NV) is 0.01% by mass to50% by mass and the rest is an aqueous solvent (water or a mixture ofwater and the organic solvent) or in an embodiment where the rest is anaqueous solvent and a volatile compound (e.g. ammonia). An embodimentwherein the NV is 0.05% by mass to 40% by mass is more preferable. Thenon-volatile content (NV) refers to the mass proportion of residueremaining in the polishing composition after drying the polishingcomposition at 105° C. for 24 hours.

<1-3. Abrasive>

The polishing composition disclosed herein typically comprises anabrasive. The material and properties of the abrasive in the polishingcomposition disclosed herein are not particularly limited and can besuitably selected in accordance with the purpose and application of thepolishing composition, etc. Examples of the abrasive include inorganicgrains, organic grains and organic/inorganic composite grains. Specificexamples of inorganic grains include oxide grains such as silica grains,alumina grains, cerium oxide grains, chromium oxide grains, titaniumdioxide grains, zirconium oxide grains, magnesium oxide grains,manganese dioxide grains, zinc oxide grains, red oxide grains, etc.;nitride grains such as silicon nitride grains, boron nitride grains,etc.; carbide grains such as silicon carbide grains, boron carbidegrains, etc.; diamond grains; carbonates such as calcium carbonate,barium carbonate, etc.; and the like. Specific examples of organicgrains include polymethyl methacrylate (PMMA) grains, poly(meth)acrylicacid grains (herein the (meth)acrylic acid comprehensively means acrylicacid and methacrylic acid), polyacrylonitrile grains, and the like.These abrasives can be used singly as one species or in a combination oftwo or more species.

As the abrasive, inorganic grains are preferable. In particular, grainsof an oxide of a metal or metalloid are preferable. Preferable examplesof the abrasive that can be used in the art disclosed herein includesilica grains. For instance, the use of silica grains as the abrasive isparticularly preferable when applying the art disclosed herein to apolishing composition that can be used for polishing a silicon wafer.This is because when the polished article is a silicon wafer, the use ofsilica grains formed of oxygen atoms and the same element as thepolished article will not leave metal or metalloid residues that are notsilicon after the polishing, eliminating risks such as contamination ofthe silicon wafer surface and degradation of electrical properties ofthe silicon wafer caused by dispersion of metal or metalloid residuesthat are not silicon in the polished article. In addition, becausesilicon and silica are similar in hardness, polishing can be performedon a silicon wafer surface without causing excessive damage. An exampleof an embodiment of the polishing composition preferable from such astandpoint is a polishing composition comprising the abrasive consistingof silica grains. By nature, silica can be readily obtained in a highlypure state. This is also one of the reasons that silica grains arepreferable as the abrasive. Specific examples of silica grains includecolloidal silica, fumed silica, precipitated silica and the like. Fromthe standpoint of the less likelihood of scratching the polishing objectsurface and capability of making a surface with lower haze, colloidalsilica and fumed silica are cited as preferable silica grains. Colloidalsilica is particularly preferable. For instance, colloidal silica ispreferably used as the abrasive in the polishing composition used forpolishing (especially, final polishing) of a silicon wafer.

The silica constituting the silica grains has a true specific gravity ofpreferably 1.5 or higher, more preferably 1.6 or higher, or yet morepreferably 1.7 or higher. With increasing true specific gravity of thesilica, the polishing rate (amount of surface removed from articlesurface per unit time) may increase when polishing a polishing object(e.g. silicon wafer). From the standpoint of reducing scratchesoccurring in the surface (polished surface) of the polishing object,preferable silica grains have a true specific gravity of 2.2 or lower.As the true specific gravity of the silica, the value measured by aliquid displacement method using ethanol as the displacing liquid can beused.

In the art disclosed herein, the abrasive in the polishing compositioncan be in a form of primary particles or in a form of secondaryparticles which are aggregates of primary particles. Alternatively, theabrasive may be present both in the primary particle form and secondaryparticle form. In a preferable embodiment, the abrasive is present atleast partially in a secondary particle form in the polishingcomposition.

The average primary particle diameter D_(P1) is not particularlylimited. From the standpoint of the polishing efficiency, etc., it ispreferably 5 nm or larger, or more preferably 10 nm or larger. From thestandpoint of obtaining greater effects of polishing (e.g. effects suchas reduced haze, removal of defects, etc.), the average primary particlediameter D_(P1) is preferably 15 nm or larger, or more preferably 20 nmor larger (e.g. larger than 20 nm). From the standpoint of thelikelihood of yielding a highly smooth surface, the abrasive has anaverage primary particle diameter D_(P1) of preferably 100 nm orsmaller, more preferably 50 nm or smaller, or yet more preferably 40 nmor smaller. From the standpoint of the likelihood of obtaining ahigher-quality surface (e.g. a surface with reduced defect such as LPD,PID (polishing induced effect), etc.), the art disclosed herein can alsobe preferably implemented in an embodiment using an abrasive having anaverage primary particle diameter D_(P1) of 35 nm or smaller (typicallysmaller than 35 nm, more preferably 32 nm or smaller, e.g. smaller than30 nm).

In the art disclosed herein, the abrasive's average primary particlediameter D_(P1) can be determined, for instance, from the specificsurface area S (m²/g) measured by the BET method, based on the equationfor the average primary particle diameter D_(P1) (nm)=2727/S. Theabrasive's specific surface area can be measured by using, for instance,a surface area analyzer under trade name “FLOW SORB 112300” availablefrom Micromeritics.

The average secondary particle diameter D_(P2) of the abrasive is notparticularly limited. From the standpoint of the polishing rate, etc.,it is preferably 10 nm or larger, or more preferably 20 nm or larger.From the standpoint of obtaining greater effects of polishing, theaverage secondary particle diameter D_(P2) is preferably 30 nm orlarger, more preferably 35 nm or larger, or yet more preferably 40 nm orlarger (e.g. larger than 40 nm). From the standpoint of yielding ahighly smooth surface, the abrasive has an average secondary particlediameter D_(P2) of suitably 200 nm or smaller, preferably 150 nm orsmaller, or more preferably 100 nm or smaller. From the standpoint ofthe likelihood of obtaining a higher-quality surface (e.g. a surfacewith reduced defect such as LPD, PID, etc.), the art disclosed hereincan also be preferably implemented in an embodiment using an abrasivehaving an average secondary particle diameter D_(P2) of smaller than 60nm (more preferably 55 nm or smaller, e.g. smaller than 50 nm).

The abrasive's average secondary particle diameter D_(P2) can bemeasured for an aqueous dispersion of the abrasive of interest(dispersion having a water-soluble polymer-free composition) as ameasurement sample by dynamic light scattering using, for instance,model “UPA-UT151” available from Nikkiso Co., Ltd.

The abrasive's average secondary particle diameter D_(P2) is generallyequal to or larger than the abrasive's average primary particle diameterD_(P1) (D_(P2)/D_(P1)>1) and is typically larger than D_(P1)(D_(P2)/D_(P1)>1). Although not particularly limited, from thestandpoint of the effects of polishing and post-polishing surfacesmoothness, D_(P2)/D_(P1) of the abrasive is usually suitably in a rangeof 1.2 to 3, preferably in a range of 1.5 to 2.5, or more preferably ina range of 1.7 to 2.3 (e.g. 1.8 or greater, but 2.2 or less).

The abrasive grain may have a globular shape (external shape) or anon-globular shape. Specific examples of non-globular shapes of theabrasive include a peanut shape (i.e. peanut shell shape), cocoon shape,confeito shape (spiky ball shape), rugby ball shape, and so on. Forinstance, an abrasive mostly comprising peanut-shaped grains can bepreferably used.

Although not particularly limited, the abrasive has an average value ofprimary particle's major axis to minor axis ratio (average aspect ratio)of theoretically 1.0 or greater, preferably 1.05 or higher, or morepreferably 1.1 or higher. With increasing average aspect ratio of theabrasive, a higher polishing rate can be obtained. From the standpointof scratch reduction and so on, the abrasive's average aspect ratio ispreferably 3.0 or lower, more preferably 2.0 or lower, or yet morepreferably 1.5 or lower.

The abrasive's shape (external shape) and average aspect ratio can beassessed, for instance by electron microscope observations. In specificprocedures for determining the average aspect ratio, for instance, usinga scanning electron microscope (SEM), with respect to a prescribednumber (e.g. 200) of abrasive grains having observable separate shapes,the smallest circumscribing rectangles are drawn on the respective grainimages. With respect to the rectangle drawn on each grain image, thelong side length (major axis length) is divided by the short side length(minor axis length) to determine the major axis/minor axis ratio (aspectratio). The aspect ratios of the prescribed number of grains can bearithmetically averaged to determine the average aspect ratio.

<1-4. Basic Compound>

The polishing compound disclosed herein typically comprises a basiccompound. In the present specification, the basic compound refers to acompound that dissolves in water and increase the pH of the resultingaqueous solution. In typical, it refers to a compound capable ofincreasing the pH of a polishing composition when added to thecomposition. The basic compound may work to chemically polish the targetsurface and contribute to increase the polishing rate. The basiccompound may also help increase the dispersion stability of thepolishing composition (especially a polishing composition comprising anabrasive).

As the basic compound, organic or inorganic nitrogen-containing basiccompounds, hydroxides of alkali metals or alkaline earth metals, variouscarbonates and hydrogen carbonates, etc., can be used. Examples includealkali metal hydroxides; quaternary ammonium hydroxides and saltsthereof; ammonia; amines; and the like. Specific examples of alkalimetal hydroxides include potassium hydroxide, sodium hydroxide, etc.Specific examples of carbonates and hydrogen carbonates include ammoniumhydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate,potassium carbonate, sodium hydrogen carbonate, sodium carbonate, etc.Specific examples of quaternary ammonium hydroxides or salts thereofinclude such as tetramethylammonium hydroxide, tetraethylammoniumhydroxide, tetrabutylammonium hydroxide, etc. Specific examples ofamines include methylamine, dimethylamine, trimethylamine, ethylamine,diethylamine, triethylamine, ethylenediamine, monoethanolamine,N-(3-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine,triethylenetetraamine, anhydrous piperazine, piperazine hexahydrate,1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, azoles suchas imidazole, triazole, etc.; and the like. These basic compounds can beused singly as one species or in a combination of two or more species.

Examples of basic compounds preferable from the standpoint of increasingthe polishing rate, etc., include ammonia, potassium hydroxide, sodiumhydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide,ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogencarbonate, potassium carbonate, sodium hydrogen carbonate and sodiumcarbonate. In particular, preferable examples include ammonia, potassiumhydroxide, sodium hydroxide, tetramethylammonium hydroxide andtetraethylammonium hydroxide. As more preferable species, ammonia andtetramethylammonium hydroxide are cited. An especially preferable basiccompound is ammonia.

<1-5. Surfactant>

The polishing composition disclosed herein can be preferably made in anembodiment comprising a surfactant (typically a water-soluble organiccompound having a molecular weight below 1×10⁴) as necessary. The use ofsurfactant may increase the dispersion stability of the polishingcomposition (especially a polishing composition comprising an abrasive).It may facilitate the reduction of haze. For the surfactant, solely onespecies or a combination of two or more species can be used.

As the surfactant, anionic or nonionic kinds can be preferably used.From the standpoint of the low-foaming properties and easy pHadjustment, nonionic surfactants are more preferable. Examples includeoxyalkylene polymers such as polyethylene glycol, polypropylene glycol,polytetramethylene glycol, etc.; polyoxyalkylene adducts such aspolyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether,polyoxyethylene alkylamine, polyoxyethylene fatty acid esters,polyoxyethylene glyceryl ether fatty acid esters, polyoxyethylenesorbitan fatty acid esters, etc.; copolymers (diblock copolymers,triblock copolymers, random-type copolymers, alternating-typecopolymers) of a plurality of species of oxyalkylene; and the like.

Specific examples of nonionic surfactant include a block copolymer of EOand PO (diblock copolymer, PEO-PPO-PEO triblock copolymer, PPO-PEO-PPOtriblock copolymer, etc.), a random copolymer of EO and PO,polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylenebutyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether,polyoxyethylene octyl ether, polyoxyethylene 2-ethylhexyl ether,polyoxyethylene nonyl ether, polyoxyethylene decyl ether,polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether,polyoxyethylene lauryl ether, polyoxyethylene cetyl ether,polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether,polyoxyethylene oleyl ether, polyoxyethylene phenyl ether,polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether,polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenylether, polyoxyethylene laurylamine, polyoxyethylene stearylamine,polyoxyethylene oleylamine, polyoxyethylene stearylamide,polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylenemonostearate, polyoxyethylene distearate, polyoxyethylene monooleate,polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate,polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitanmonostearate, polyoxyethylene sorbitan monooleate,polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitol tetraoleate,polyoxyethylene castor oil, polyoxyethylene hardened castor oil, and thelike. Particularly preferable surfactants include a block copolymer ofEO and PO (especially a PEO-PPO-PEO triblock copolymer), a randomcopolymer of EO and PO, and polyoxyethylene alkyl ether (e.g.polyoxyethylene decyl ether).

The surfactant typically has a molecular weight below 1×10⁴. From thestandpoint of the ease of filtering the polishing composition andwashing the polished article, it is preferably 9500 or smaller. Themolecular weight of the surfactant is typically 200 or larger. From thestandpoint of haze reduction effect, etc., it is preferably 250 orlarger, or more preferably 300 or larger (e.g. 500 or larger). As themolecular weight of the surfactant, the weight average molecular weight(Mw) determined by GPC (aqueous, based on standard polyethylene glycol)or the molecular weight determined from the chemical formula can beused.

More preferable molecular weight ranges of the surfactant may also varydepending on the type of surfactant. For instance, when a blockcopolymer of EO and PO is used as the surfactant, its Mw is preferably1000 or larger, more preferably 2000 or larger, or yet more preferably5000 or larger.

<1-6. Optional Polymers>

In addition to the water-soluble polymer described above (typically, awater-soluble polymer comprising repeat units A and B), the polishingcomposition disclosed herein may further comprise, as necessary, anotherwater-soluble polymer (or an “optional polymer” hereinafter) having anMw of 1×10⁴ or larger. The type of such optional polymer is notparticularly limited. A suitable species can be selected amongwater-soluble polymers that are known in the field of polishingcompositions, but do not belong to the aforementioned water-solublepolymer.

The optional polymer may have, in its molecule, at least one species offunctional group selected among cationic groups, anionic groups andnonionic groups. The optional polymer may have, in its molecule, ahydroxyl group, carboxyl group, acyloxy group, sulfo group, amidestructure, quaternary nitrogen structure, heterocyclic structure, vinylstructure, polyoxyalkylene structure, etc. From the standpoint ofreducing aggregates or increasing the washability, etc., a nonionicpolymer can be preferably used as the optional polymer.

Preferable examples of the optional polymer in the polishing compositiondisclosed herein include an oxyalkylene unit-containing polymer,nitrogen atom-containing polymer, polyvinyl alcohol having a degree ofsaponification of 95% by mole or higher, and the like.

Examples of the oxyalkylene unit-containing polymer include polyethyleneoxide (PEO), a block copolymer of ethylene oxide (EO) and propyleneoxide (PO), a random copolymer of EO and PO, etc. The EO/PO blockcopolymer can be a diblock copolymer, triblock copolymer, etc.,comprising a polyethylene oxide (PEO block and a polypropylene oxide(PPO) block. Examples of the triblock copolymer include a PEO-PPO-PEOtriblock copolymer and PPO-PEO-PPO triblock copolymer. Usually, aPEO-PPO-PEO triblock copolymer is more preferable. In the block orrandom copolymer of EO and PO, from the standpoint of the watersolubility and washability, etc., the molar ratio (EO/PO) between EO andPO constituting the copolymer is preferably higher than 1, morepreferably 2 or higher, or yet more preferably 3 or higher (e.g. 5 orhigher).

As the nitrogen atom-containing polymer, either a polymer comprisingnitrogen atoms in the main chain or a polymer having a nitrogen atom ina side chain (pendant group) can be used. Examples of the polymer havinga nitrogen atom in the main chain include a homopolymer and a copolymerof an N-acylalkyleneimine-based monomer. Specific examples of theN-acylalkyleneimine-based monomer include N-acetylethyleneimine,N-propionylethyleneimine, etc. Examples of the polymer having a nitrogenatom in a pendant group include a polymer comprising an N-(meth)acryloylmonomeric unit, a polymer comprising an N-vinyl monomeric unit, etc. Theterm “(meth)acryloyl” herein comprehensively refers to acryloyl andmethacryloyl. For example, a homopolymer and a copolymer ofN-(meth)acryloylmorpholine, a homopolymer and a copolymer ofN-vinylpyrrolidone, etc., can be used. Unless otherwise indicated, thecopolymer in this specification comprehensively means various copolymerssuch as random copolymer, alternating copolymer, block copolymer, graftcopolymer, etc.

When a polyvinyl alcohol is used as an optional polymer, a preferablespecies as the polyvinyl alcohol has a degree of saponification of 95%by mole or higher (e.g. higher than 98% by mole). The degree ofsaponification of a polyvinyl alcohol is theoretically 100% by mole orlower.

Other examples of the optional polymer that can be contained in thepolishing composition disclosed herein include cellulose derivativessuch as hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethylmethylcellulose, hydroxypropyl methylcellulose, methylcellulose,ethylcellulose, ethylhydroxyethyl cellulose, carboxymethyl cellulose,etc.; and pullulan.

The molecular weight and the molecular weight distribution (Mw/Mn) ofthe optional polymer are not particularly limited. For example, thepreferable Mw and molecular weight distribution of the aforementionedwater-soluble polymer can be also applied to the Mw and molecular weightdistribution of the optional polymer.

The optional polymer is used in an amount of suitably 30% by mass orless of the total amount of water-soluble components with Mw of 1×10⁴ orlarger (including the aforementioned water-soluble polymer and optionalpolymers used as necessary), preferably 15% by mass or less, or morepreferably 10% by mass or less (e.g. 5% by mass or less). The polishingcomposition disclosed herein can be preferably made in an embodimentessentially free of optional polymers (e.g. the optional polymer contentin the total amount of water-soluble components is less than 1% by massor non-detectable).

When the polishing composition disclosed herein comprises a cellulosederivative as an optional polymer, its amount used is preferably as lowas or lower than 10% by mass of the total amount of water-solublecomponents with Mw of 1×10⁴ or larger in the polishing composition, ormore preferably 5% by mass or less (typically 1% by mass or less). Bythis, inclusion of contamination and aggregation caused by the use of anatural compound-derived cellulose derivative can be reduced to agreater extent. The polishing composition disclosed herein can bepreferably made, for instance, in an embodiment essentially free of acellulose derivative (e.g. the cellulose derivative content in the totalamount of the water-soluble components is less than 1% by mass ornon-detectable).

The art disclosed herein can be implemented in an embodiment of thepolishing composition that comprises a water-soluble polymer Q whilesatisfying the following conditions: having a Mw of 1×10⁴ or larger;comprising a hydroxyl group-containing repeat unit h; and having ahydroxyl group content in a range of 4 mmol/g or higher, but 21 mmol/gor lower. The water-soluble polymer Q may be a water-soluble polymerthat comprises the aforementioned repeat units A and B or may be apolymer that belongs to the optional polymer. A polishing compositioncomprising such a water-soluble polymer Q is preferably supplied to apolishing object with the hydroxyl group content of the water-solublepolymer being maintained in a range from 4 mmol/g up to 21 mmol/g whenused for polishing the polishing object. The repeat unit h can be, forinstance, a vinyl alcohol unit.

In this specification, the hydroxyl group content refers to the numberof moles of hydroxyl groups contained in one gram of the polymer. Thehydroxyl group content can be generally obtained by subjecting a samplesolution comprising the polymer of interest to neutralization titrationas specified in JIS K0070 to determine the hydroxyl value (mgKOH/g) anddividing the hydroxyl value by 56.1. When the polymer of interest is,for instance, a polymer formed of vinyl carboxylate units and vinylalcohol units such as a partially-saponified polyvinyl alcohol,potassium hydroxide (KOH) is added to the sample solution containing thepolymer of interest and the resulting solution is heated to allowcomplete saponification; the amount of KOH consumed during this isdetermined by titration; from the results, the number of moles of vinylcarboxylate units and the number of moles of vinyl alcohol units aredetermined; and from their numbers of moles, the hydroxyl group contentcan be determined.

In measuring the hydroxyl group content, when a polymer contained in apolishing composition is measured, the polishing composition can be usedas the sample solution. When the polishing composition comprises anabrasive, the abrasive is precipitated by centrifugation and theresulting supernatant can be used as the sample solution.

<1-7. Other Components>

As far as the effects by the present invention are not significantlyhindered, the polishing composition disclosed herein may furthercomprise as necessary known additives, such as chelating agents, organicacids, organic acid salts, inorganic acids, inorganic acid salts,preservatives, antifungal agents, and so on, usable in polishingcompositions (typically, polishing compositions used for final polishingof silicon wafers).

Examples of chelating agents include aminocarboxylic acid-basedchelating agents and organophosphonic acid-based chelating agents.Examples of aminocarboxylic acid-based chelating agents includeethylenediamine tetraacetic acid, ethylenediamine tetraacetic acidsodium salt, nitrilotriacetic acid, nitrilotriacetic acid sodium salt,nitrilotriacetic acid ammonium salt, hydroxyethylethylenedimainetriacetic acid, hydroxyethylethylenediamine triacetic acid sodium salt,diethylenetriamine pentaacetic acid, diethylenetriamine pentaacetic acidsodium salt, triethylenetetramine hexaacetic acid, andtriethylenetetramine hexaacetic acid sodium salt. Examples oforganophosphonic acid-based chelating agents include2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid,aminotri(methylenephosphonic acid),ethylenediaminetetrakis(methylenephosphonic acid),diethylenetriaminepenta(methylenephosphonic acid),ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid,ethane-1-hydroxy-1,1-diphosphonic acid,ethane-1-hydroxy-1,1,2-triphosphonic acid,ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonicacid, 2-phosphonobutane-1,2-dicarboxylic acid,1-phosphonobutane-2,3,4-tricarboxylic acid, andα-methylphosphonosuccinic acid. Among them, organophosphonic acid-basedchelating agents are preferable, withethylenediaminetetrakis(methylenephosphonic acid) anddiethylenetriaminepenta(methylenephosphonic acid) being more preferable.A particularly preferable chelating agent isethylenediaminetetrakis(methylenephosphonic acid).

Examples of organic acids include aliphatic acids such as formic acid,acetic acid, propionic acid, etc.; aromatic carboxylic acids such asbenzoic acid, phthalic acid, etc.; as well as citric acid, oxalic acid,tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid,organic sulfonic acids, organic phosphoric acids, and the like. Examplesof organic acid salts include alkali metal salts (sodium salts,potassium salts, etc.), ammonium salts and the like of organic acids.Examples of inorganic acids include sulfuric acid, nitric acid,hydrochloric acid, carbonic acid, etc. Examples of inorganic acid saltsinclude alkali metal salts (sodium salts, potassium salts, etc.) andammonium salts of inorganic acids. The organic acids and their salts aswell as inorganic acids and their salts can be used singly as onespecies or in a combination of two or more species.

Examples of preservatives and antifungal agents includeisothiazoline-based compounds, paraoxybenzoic acid esters,phynoxyethanol, etc.

<1-8. Applications>

The polishing composition disclosed herein can be suitably applied forpolishing objects of various materials and shapes. The polishingobject's material can be, for instance, a metal or metalloid such assilicon, aluminum, nickel, tungsten, copper, tantalum, titanium,stainless steel, etc., or an alloy of these; a glassy material such asquartz glass, aluminosilicate glass, glassy carbon, etc.; a ceramicmaterial such as alumina, silica, sapphire, silicon nitride, tantalumnitride, titanium carbide, etc.; a material for compound semiconductorsubstrates such as silicon carbide, gallium nitride, gallium arsenide,etc.; a resin material such as polyimide resin, etc.; or the like. Thepolishing object may be formed of several materials among them. Inparticular, it is suitable for polishing a polishing object having asurface formed of silicon. The art disclosed herein can be particularlypreferably applied to a polishing composition comprising silica grains(typically consisting of silica grains) as the abrasive and intended forpolishing silicon.

The shape of the polishing object is not particularly limited. Thepolishing composition disclosed herein can be preferably applied forpolishing a polishing object having a flat surface such as a plate,polyhedron, etc.

The polishing composition disclosed herein can be preferably used forfinal polishing of a polishing object. Accordingly, this specificationprovides a polished article production method (e.g. silicon waferproduction method) comprising a final polishing step using the polishingcomposition. The final polishing refers to the last polishing step (i.e.a step after which no further polishing is performed) in a productionprocess of a polishing object of interest. The polishing compositiondisclosed herein may be used in an earlier polishing step than finalpolishing (referring to a step between the rough polishing step andfinal polishing step, typically including at least a first polishingstep and possibly second, third . . . polishing steps), for instance, ina polishing step performed just before final polishing.

The polishing composition disclosed herein can be preferably used forpolishing a surface formed of silicon and particularly preferably usedfor polishing a silicon wafer. For instance, it is preferable as apolishing composition used in final polishing of a silicon wafer or inan earlier polishing step than this. For instance, it is effectivelyapplied for polishing (typically final polishing or polishing justbefore this) of a silicon wafer prepared into a surface state having asurface roughness of 0.01 nm to 100 nm in an earlier step. It isparticularly preferably applied to final polishing.

<1-9. Polishing Liquid>

The polishing composition disclosed herein is supplied to a polishingobject, typically in a form of a polishing liquid comprising thepolishing composition, and used for polishing the polishing object. Thepolishing liquid may be prepared, for instance, by diluting (typicallywith water) a polishing composition disclosed herein. Alternatively, thepolishing composition can be used straight as a polishing liquid. Inother words, the concept of polishing composition in the art disclosedherein encompasses both a polishing liquid (working slurry) supplied toa polishing object and used for polishing the polishing object and aconcentrate (stock solution of polishing liquid) which is diluted foruse as a polishing liquid. Other examples of the polishing liquidcomprising the polishing composition disclosed herein include apolishing liquid obtained by adjusting the pH of the composition.

The water-soluble polymer content in the polishing liquid is notparticularly limited. For instance, it can be 1×10⁻⁴% by mass or higher.From the standpoint of haze reduction, etc., the polymer content ispreferably 5×10⁻⁴% by mass or higher, or more preferably 1×10⁻³% by massor higher, for instance, 2×10⁻³% by mass or higher. From the standpointof the polishing rate, etc., the polymer content is preferably 0.2% bymass or lower, or more preferably 0.1% by mass or lower (e.g. 0.05% bymass or lower).

When the polishing composition comprises an abrasive, the abrasivecontent in the polishing liquid is not particularly limited. It istypically 0.01% by mass or higher, preferably 0.05% by mass or higher,or more preferably 0.1% by mass or higher, for instance, 0.15% by massor higher. With increasing abrasive content, a higher polishing rate canbe obtained. From the standpoint of obtaining a surface with lower haze,usually, the abrasive content is suitably 10% by mass or lower,preferably 7% by mass or lower, more preferably 5% by mass or lower, oryet more preferably 2% by mass or lower, for instance, 1% by mass orlower.

When a basic compound is contained, the basic compound content in thepolishing liquid is not particularly limited. From the standpoint ofincreasing the polishing rate, etc., usually, the basic compound contentis preferably 0.001% by mass or more of the polishing liquid, or morepreferably 0.003% by mass or more. From the standpoint of hazereduction, etc., the basic compound content is preferably below 0.4% bymass, or more preferably below 0.25% by mass.

The pH of the polishing liquid is not particularly limited. Forinstance, the pH is preferably 8.0 or more, or more preferably 9.0 ormore, but preferably 12.0 or less, or more preferably 11.0 or less. Itis preferable that the basic compound is contained to yield such a pH ofthe polishing liquid. The pH can be preferably applied to a polishingliquid (e.g. polishing liquid for final polishing) used for polishing asilicon wafer.

When the polishing composition disclosed herein comprises a surfactant,the surfactant content in the polishing liquid is not particularlylimited. For instance, it can be 1×10⁻⁴% by mass or higher. From thestandpoint of haze reduction, etc., a preferable surfactant content is5×10⁻⁴% by mass or higher, or more preferably 1×10⁻³% by mass or higher,for instance, 2×10⁻³% by mass or higher. From the standpoint of thewashability, polishing rate, etc., the surfactant content is preferably0.2% by mass or lower, or more preferably 0.1% by mass or lower (e.g.0.05% by mass or lower).

When the polishing composition disclosed herein comprises a surfactant,the mass ratio of water-soluble polymer content w1 to surfactant contentw2 is not particularly limited. For instance, the mass ratio w1/w2 canbe 0.01 or more, or preferably 0.05 or more, or more preferably 0.1 ormore, but 100 or less, or preferably 50 or less, or more preferably 30or less.

When the polishing composition disclosed herein is used in a polishingliquid form comprising an abrasive, the surfactant content relative to100 parts by mass of the abrasive is suitably, for instance, 20 parts bymass or less, preferably 15 parts by mass or less, or more preferably 10parts by mass or less (e.g. 6 parts by mass or less). From thestandpoint of obtaining greater effect of the surfactant use, thesurfactant content relative to 100 parts by mass of the abrasive issuitably 0.001 part by mass or greater, preferably 0.005 part by mass orgreater, or more preferably 0.01 part by mass or greater (e.g. 0.1 partby mass or greater).

Alternatively, from the standpoint of simplifying the composition, etc.,the polishing composition disclosed herein can be preferably made in anembodiment essentially free of a surfactant.

<1-10. Concentrate>

The polishing composition disclosed herein may be in a concentrated form(i.e. in a form of a concentrate of the polishing liquid) beforesupplied to a polishing object. The polishing composition in aconcentrated form as this is advantageous from the standpoint of theconvenience and cost reduction for production, distribution, storage,etc. The concentration can be, for instance, about 2-fold or more, orusually suitably about 5-fold or more, but 100-fold or less, or usuallysuitably about 50-fold or less. The concentration of the polishingcomposition according to a preferable embodiment is, 10-fold or more,for instance, 15-fold or more, but 40-fold or less, for instance,25-fold or less.

The polishing composition in a concentrated form as this can be used inan embodiment where it is diluted whenever desired to prepare apolishing liquid and the polishing liquid is supplied to a polishingobject. The dilution can be carried out typically by adding anaforementioned aqueous solvent to the concentrate and mixing. When theaqueous solvent is a solvent mixture, the dilution can be performed byadding just some of the components of the aqueous solvent or by adding asolvent mixture comprising the components at a mass ratio different fromthat of the aqueous solvent. With respect to a multiple-part typepolishing composition as described later, some of the parts may bediluted first and then mixed with other parts to prepare a polishingliquid, the multiple parts may be mixed first followed by dilution ofthe mixture to prepare a polishing liquid.

The concentrate can have an NV of, for instance, 50% by mass or lower.From the standpoint of the stability (e.g. dispersion stability of theabrasive) and ease of filtration of the polishing composition, etc.,usually, the concentrate has an NV of suitably 40% by mass or lower,preferably 30% by mass or lower, or yet more preferably 20% by mass orlower, for instance, 15% by mass or lower. From the standpoint of theconvenience and cost reduction for production, distribution, storage andso on, the NV of the concentrate is suitably 0.5% by mass or higher,preferably 1% by mass or higher, or more preferably 3% by mass orhigher, for instance, 5% by mass or higher.

The water-soluble polymer content in the concentrate can be, forinstance, 3% by mass or lower. From the standpoint of the ease offiltration and washability of the polishing composition, etc., usually,the water-soluble polymer content is preferably 1% by mass or lower, ormore preferably 0.5% by mass or lower. From the standpoint of theconvenience and cost reduction for production, distribution, storage andso on, the water-soluble polymer content is usually suitably 1×10⁻³% bymass or higher, preferably 5×10⁻³% by mass or higher, or more preferably1×10⁻²% by mass or higher.

When the polishing composition disclosed herein comprises an abrasive,the abrasive content in the concentrate can be, for instance, 50% bymass or lower. From the standpoint of the stability (e.g. dispersionstability of the abrasive) and ease of filtration of the polishingcomposition, etc., usually, the abrasive content is preferably 45% bymass or lower, or more preferably 40% by mass or lower. In a preferableembodiment, the abrasive content can be 30% by mass or lower, or even20% by mass or lower (e.g. 15% by mass or lower). From the standpoint ofthe convenience and cost reduction for production, distribution, storageand so on, the abrasive content can be, for instance, 0.5% by mass orhigher, preferably 1% by mass or higher, or more preferably 3% by massor higher (e.g. 5% by mass or higher).

The polishing composition disclosed herein may be of a one-part type ora multiple-part type such as the two-part type. For example, it may beformulated such that agent A (e.g. a basic abrasive dispersion describedlater) that comprises some of the components of the polishingcomposition and agent B (e.g. an aqueous polymer solution describedlater) that comprises the rest of the components are mixed and themixture is used for polishing of a polishing object.

<1-11. Preparation of Polishing Composition>

The method for producing the polishing composition disclosed herein isnot particularly limited. For instance, the respective components of thepolishing composition can be mixed, using a commonly known mixing devicesuch as a propeller stirrer, ultrasonic disperser, homo mixer, etc. Theway of mixing these components is not particularly limited. Forinstance, all the components can be mixed at once or in a suitablyselected order.

Although not particularly limited, with respect to a polishingcomposition comprising a water-soluble polymer, an abrasive and a basiccompound, from the standpoint of consistently (reproducibly) producingpolishing compositions having less aggregates, can be preferably used,for instance, a production method comprising obtaining a dispersioncomprising an abrasive (e.g. silica grains), a basic compound and water(or a “basic abrasive dispersion” hereinafter) and mixing the basicabrasive dispersion and a water-soluble polymer.

In such a basic abrasive dispersion where the abrasive and basiccompound are co-present, the abrasive exhibits greater electrostaticrepulsion due to the basic compound and thus shows higher dispersionstability than a basic compound-free abrasive dispersion (typicallyalmost neutral). Accordingly, local aggregation of the abrasive is lesslikely to occur as compared with an embodiment where the basic compoundis added after addition of the water-soluble polymer to a neutralabrasive dispersion and an embodiment where the neutral abrasivedispersion, water-soluble polymer and basic compound are mixed all atonce. This is preferable from the standpoint of increasing the ease offiltration of the polishing composition or reducing defects in thepolished surface, etc.

The water-soluble polymer is preferably pre-dissolved in water and mixedin the form of an aqueous solution (or “aqueous polymer solution”hereinafter) with the basic abrasive dispersion. This can better inhibitlocal aggregation of the abrasive.

When mixing the basic abrasive dispersion and aqueous polymer solution,it is preferable to add the aqueous polymer solution to the basicabrasive dispersion. According to such a mixing method, localaggregation of the abrasive can be better prevented, for instance, ascompared with a mixing method where the basic abrasive dispersion isadded to the aqueous polymer solution. When the abrasive is silicagrains (e.g. colloidal silica grains), it is particularly meaningful touse the mixing method by which an aqueous polymer solution is added to abasic abrasive dispersion as described above.

Among the abrasive, the water-soluble polymer, the basic compound andwater forming the polishing composition to be produced, the basicabrasive dispersion comprises at least some of the abrasive, at leastsome of the basic compound and at least some of the water. For instance,in a preferable embodiment, the abrasive dispersion comprises all theabrasive forming the polishing composition, at least some of the basiccompound and at least some of the water.

The basic compound content in the basic abrasive dispersion ispreferably 0.01% by mass or greater, more preferably 0.05% by mass orgreater, or yet more preferably 0.1% by mass or greater. With increasingbasic compound content, there is a tendency for greater inhibition ofthe occurrence of local aggregation during preparation of the polishingcomposition. The basic compound content in the basic abrasive dispersionis preferably 10% by mass or less, more preferably 5% by mass or less,or yet more preferably 3% by mass or less. A lower basic compoundcontent facilitates adjustment of the basic compound content in thepolishing composition.

The basic abrasive dispersion has a pH of preferably 8 or higher, ormore preferably 9 or higher. With increasing pH, there is a tendency forgreater inhibition of the occurrence of local aggregation when thewater-soluble polymer or an aqueous solution thereof is added to thebasic abrasive dispersion. The pH of the basic abrasive dispersion ispreferably 12 or lower, more preferably 11.5 or lower, or yet morepreferably 10.5 or lower. With the pH of the basic abrasive dispersionbeing lower in a pH range of 7 or higher, the amount of the basiccompound required for preparing the dispersion is reduced, making iteasier to adjust the basic compound content in the polishingcomposition. For instance, when the abrasive is silica grains, it isalso advantageous that the pH is not excessively high, from thestandpoint of reducing dissolution of the silica. The mixture's pH canbe adjusted by modifying the amount of the basic compound added, etc.

Such a basic abrasive dispersion can be prepared by mixing an abrasive,a basic compound and water. They can be mixed with a commonly knownmixing device such as a propeller stirrer, ultrasonic disperser, homomixer, etc. The mode of mixing the respective components of the basicabrasive dispersion is not particularly limited. For instance, thecomponents can be mixed all at once or in a suitably selected order. Anexample of preferable embodiments is an embodiment where anapproximately neutral dispersion comprising the abrasive and water ismixed with the basic compound or an aqueous solution thereof.

When mixing the water-soluble polymer in a form of an aqueous solution(aqueous polymer solution) into a basic abrasive dispersion, thewater-soluble polymer content in the aqueous polymer solution ispreferably 0.02% by mass or greater, more preferably 0.05% by mass orgreater, or yet more preferably 0.1% by mass or greater. With increasingwater-soluble polymer content, it becomes easier to adjust thewater-soluble polymer content in the polishing composition. Thewater-soluble polymer content in the aqueous polymer solution ispreferably 10% by mass or less, more preferably 5% by mass or less, oryet more preferably 3% by mass or less. With decreasing water-solublepolymer content, local aggregation of the abrasive tends to be morelikely reduced when mixing the aqueous polymer solution with the basicabrasive dispersion.

The pH of the aqueous polymer solution is not particularly limited andcan be adjusted, for instance, to pH 2 to 11. The pH of the aqueouspolymer solution is adjusted preferably to around neutral to basic, ormore preferably to basic. More specifically, the pH of the aqueouspolymer solution is preferably 8 or higher, or more preferably 9 orhigher. The pH can be adjusted by using some of the basic compoundforming the polishing composition. The increased pH of the aqueouspolymer solution can more greatly reduce local aggregation of theabrasive when the aqueous polymer solution is added to the basicabrasive dispersion. The pH of the aqueous polymer solution ispreferably 12 or lower, or more preferably 10.5 or lower. Withdecreasing pH of the aqueous polymer solution, the amount of the basiccompound required for preparing the aqueous polymer solution is reduced,making it easier to adjust the basic compound content in the polishingcomposition. For instance, when the abrasive is silica grains, it isadvantageous that the pH is not excessively high also from thestandpoint of reducing dissolution of the silica.

The rate (supply rate) of adding the aqueous polymer solution to thebasic abrasive dispersion is preferably, with respect to 1 L of thedispersion, at or below 500 mL of aqueous polymer solution per minute,more preferably at or below 100 mL/min, or yet more preferably at orbelow 50 mL/min. With decreasing supply rate, local aggregation of theabrasive can be more greatly reduced.

In a preferable embodiment, the aqueous polymer solution can be filteredbefore added to the basic abrasive dispersion. By filtering the aqueouspolymer solution, the amounts of contaminants and aggregates in theaqueous polymer solution can be further reduced.

The filtration method is not particularly limited. Known filtrationmethods can be suitably employed such as natural filtration performed atnormal pressure as well as suction filtration, pressure filtration,centrifugal filtration, etc. The filter used for filtration ispreferably selected based on mesh size. From the standpoint of theproductivity of polishing compositions, the filter's mesh size ispreferably 0.05 μm or larger, more preferably 0.1 μm or larger, or yetmore preferably 0.2 μm or larger. From the standpoint of increasing theeffect of eliminating contaminants and aggregates, the filter's meshsize is preferably 100 μm or smaller, more preferably 70 μm or smaller,or yet more preferably 50 μm or smaller. The filter's material orconstruction is not particularly limited. Examples of the filter'smaterial include cellulose, nylon, polysulfone, polyether sulfone,polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, glass,etc. Examples of the filter's construction include depth, pleated,membrane, etc.

The polishing composition production method described above can bepreferably applied when the polishing composition obtainable by mixingthe basic abrasive dispersion and the water-soluble polymer or anaqueous solution thereof is a polishing liquid (working slurry) or hasapproximately the same NV as this as well as when it is a concentratedescribed later.

When the water-soluble polymer is a water-soluble polymer having analkaline-hydrolytic functional group (or a “water-soluble polymer H”hereinafter), from the standpoint of obtaining greater effect of the useof the water-soluble polymer, it is preferable, but not limited to, mixa basic abrasive dispersion and an aqueous solution of the water-solublepolymer H to form a polishing liquid or a polishing composition havingapproximately the same NV as the polishing liquid (typically theabrasive content is less than 3% by mass, more preferably less than 1%by mass). Alternatively, it is preferable to mix a basic abrasivedispersion with an aqueous solution of the water-soluble polymer H andthen dilute the mixture in relatively short time from the mixing (e.g.within 24 hours after the mixing) to approximately the same NV as thepolishing liquid (typically to an abrasive content of less than 3% bymass, more preferably less than 1% by mass). A specific example of thewater-soluble polymer H is a water-soluble polymer comprising 5% by moleor more of vinyl acetate units as a repeat unit (e.g. a water-solublepolymer comprising a vinyl acetate unit and a vinyl alcohol unit asrepeat units.)

<1-12. Polishing>

The polishing composition disclosed herein can be used for polishing apolishing object, for instance, in an embodiment comprising thefollowing operations. Described below is a preferable embodiment of themethod for polishing a polishing object using the polishing compositiondisclosed herein.

In particular, a polishing liquid (which is typically a slurry polishingliquid and sometimes called a polishing slurry) is obtained, comprisinga polishing composition disclosed herein. The obtaining the polishingliquid may include, as described earlier, preparing the polishing liquidby subjecting the polishing composition to operations such asconcentration adjustment (e.g. dilution), pH adjustment, etc.Alternatively, the polishing composition can be used straight as thepolishing liquid. As for a multiple-part type polishing composition, theobtaining the polishing liquid may include obtaining the parts (agents)constituting the multiple-part type polishing composition, diluting acertain part or multiple parts prior to the mixing, diluting the mixtureafter the mixing, and so on.

Subsequently, the polishing slurry is supplied to a polishing object andpolishing is carried out by a conventional method. For instance, whencarrying out final polishing of a silicon wafer, the silicon wafer aftera lapping step and first polishing step is set in a general polishingmachine and via a polishing pad in the polishing machine, the polishingslurry is supplied to the surface (surface to be polished) of thesilicon wafer. Typically, while the polishing slurry is continuouslysupplied, the polishing pad is pushed against the surface of the siliconwafer, and the two are moved (e.g. moved in circular motion) incoordination. Via such a polishing step, polishing of the polishingobject is completed.

The polishing pad(s) used in the polishing step are not particularlylimited. For instance, any of the non-woven fabric type, suede type,abrasive-bearing type, abrasive-free type, etc., can be used.

A polishing step such as the above may be part of production processesof polished articles (e.g. substrates such as silicon wafers, etc.).Accordingly, this specification provides a method for producing apolished article (preferably, a method for producing a silicon wafer),with the method comprising the polishing step.

In a polishing step as described above, the polishing liquid supplied tothe polishing object preferably comprises the water-soluble polymerdisclosed herein (typically, a water-soluble polymer that comprises arepeat unit A and a repeat unit B). This can more suitably bring aboutthe effect of the use of the water-soluble polymer (reduction of thehaze and the number of LPD, etc.).

<1-13. Cleaning>

The polishing object polished with the polishing composition disclosedherein is typically cleaned after polished. The cleaning can be carriedout, using a suitable cleaning solution. The cleaning solution used isnot particularly limited. Usable examples include SC-1 cleaning solution(a mixture of ammonium hydroxide (NH₄OH), hydrogen peroxide (H₂O₂) andwater (H₂O); cleaning with SC-1 cleaning solution is referred to as“SC-1 cleaning” hereinafter), SC-2 cleaning solution (a mixture of HCl,H₂O₂ and H₂O) and the like generally used in the field ofsemiconductors. The temperature of the cleaning solution can be, forinstance, room temperature to about 90° C. From the standpoint ofincreasing the cleaning efficiency, a cleaning solution at about 50° C.to 85° C. can be preferably used.

<<2. Polishing Composition According to Second Aspect>>

The polishing composition according to the second aspect disclosedherein comprises an abrasive, a water-soluble polymer and water. Thepolishing composition exhibits an etching rate of 2.0 nm/min or lowerbased on the following etching rate measurement:

(1A) an etching rate measuring reagent LE is obtained, comprising 0.18%by mass of the water-soluble polymer and 1.3% by mass of ammonia withthe rest being water;

(2A) a silicon substrate (in a 6 cm long by 3 cm wide by 775 μm thickrectangle) is obtained, from which surface natural oxide film isremoved, and its mass W0 is measured;

(3A) the silicon substrate is immersed in the reagent LE at roomtemperature for 12 hours;

(4A) the silicon substrate is removed from the reagent LE and cleaned atroom temperature for 10 seconds with a cleaning solution formed of NH₃(29%)/H₂O₂(31%)/ultrapure water=1/1/8 (volume ratio);

(5A) the cleaned silicon substrate is measured for its mass W1; and

(6A) from the difference between the W0 and W1 as well as the specificgravity of the silicon substrate, the etching rate (nm/min) isdetermined;

and also has an abrasive adsorption of 20% or lower based on thefollowing abrasive adsorption measurement:

(1B) the polishing composition is centrifuged to precipitate theabrasive and the supernatant is subjected to measurement of totalorganic carbon to determine the total amount of organic carbon, C1, inthe supernatant;

(2B) a test solution L0 is obtained having the same composition as thatof the polishing composition but without the abrasive, and the testsolution L0 is subjected to measurement of total organic carbon todetermine the total amount of organic carbon, C0, in the test solutionL0; and

(3B) from the C0 and C1, the abrasive adsorption is determined by thefollowing equation:Abrasive adsorption (%)=[(C0−C1)/C0]×100

The polishing composition according to the second aspect is described indetail below.

<2-1. Water-Soluble Polymer>

The type of water-soluble polymer in the polishing composition accordingto the second aspect disclosed herein is not particularly limited. Amongwater-soluble polymers known in the field of polishing compositions, asuitable species can be selected so as to yield the prescribed etchingrate and abrasive adsorption in the polishing composition.

The water-soluble polymer may have, in its molecule, at least onespecies of functional group selected among cationic groups, anionicgroups and nonionic groups. The water-soluble polymer may have, in itsmolecule, a hydroxyl group, carboxyl group, acyloxy group, sulfo group,amide structure, quaternary nitrogen structure, heterocyclic structure,vinyl structure, polyoxyalkylene structure, etc.

A preferable example of a water-soluble polymer having an acyloxy groupin the molecule comprises at least a vinyl monocarboxylate unit.Specific examples of the vinyl monocarboxylate unit include vinylacetate unit, vinyl hexanoate unit, and the like.

A preferable example of the vinyl monocarboxylate unit-containingpolymer is a polymer comprising vinyl acetate units. In such awater-soluble polymer, the number of moles of vinyl acetate units in thetotal number of moles of all the repeat units is typically 5% orgreater, more preferably 10% or greater, yet more preferably 15% orgreater, or particularly preferably 20% or greater. The number of molesof vinyl acetate units in the total number of moles of all the repeatunits is not particularly limited. From the standpoint of the watersolubility, etc., it is usually suitably 80% or less, preferably 60% orless, more preferably 50% or less, or yet more preferably 40% or less.

Another preferable example of the vinyl monocarboxylate unit-containingwater-soluble polymer comprises vinyl hexanoate units. The number ofmoles of vinyl hexanoate units in the total number of moles of all therepeat units is typically, but not particularly limited to, 5% orgreater, more preferably 10% or greater, or yet more preferably 15% orgreater. From the standpoint of the water solubility, etc., the numberof moles of vinyl hexanoate units in the total number of moles of allthe repeat units is usually, but not particularly limited to, 80% orless, preferably 60% or less, more preferably 50% or less, or yet morepreferably 40% or less (e.g. 30% or less).

A preferable example of the water-soluble polymer having hydroxyl groupsin the molecule comprises at least vinyl alcohol units. The artdisclosed herein can be preferably implemented in an embodiment using awater-soluble polymer that comprises vinyl alcohol units and vinylacetate units. An example of such a water-soluble polymer has astructure resulting from partial saponification of vinyl acetatehomopolymer or copolymer. For instance, a partially-saponified polyvinylalcohol having a structure resulting from partial saponification ofvinyl acetate homopolymer can be preferably used. Thepartially-saponified polyvinyl alcohol is a water-soluble polymer formedof vinyl alcohol units and vinyl acetate units.

The art disclosed herein can be preferably implemented in an embodimentusing a water-soluble polymer that comprises vinyl alcohol units andvinyl hexanoate units. An example of such a water-soluble polymer has astructure resulting from partial saponification of vinyl hexanoatehomopolymer or copolymer. For instance, a partially-saponified polyvinylalcohol resulting from partial saponification of a copolymer of vinylacetate and vinyl hexanoate can be preferably used. Examples of thepartially-saponified polyvinyl alcohol include a water-soluble polymerformed of vinyl alcohol units and vinyl hexanoate units as well as awater-soluble polymer formed of vinyl alcohol units, vinyl hexanoateunits and vinyl acetate units.

From the standpoint of the water solubility, etc., as thepartially-saponified polyvinyl alcohol, a species that can be preferablyused has a degree of saponification of 50% by mole or higher (morepreferably 60% by mole or higher) while satisfying the prescribedetching rate and abrasive adsorption. From the standpoint of the etchingrate and abrasive adsorption, the partially-saponified polyvinyl alcoholhas a degree of saponification of preferably 90% by mole or lower, ormore preferably 85% by mole or lower. In a preferable embodiment, apartially-saponified polyvinyl alcohol having a degree of saponificationof 80% by mole or lower can be used. The degree of saponification of apolyvinyl alcohol is theoretically 100% by mole or lower.

From the standpoint of reducing aggregates and increasing thewashability, etc., as the water-soluble polymer, a nonionicwater-soluble polymer can be preferably used. In other words, apreferable water-soluble polymer is essentially free of anionic andcationic repeat units. Herein, being essentially free of anionic andcationic repeat units means that the molar ratio of these repeat unitsis lower than 0.02% (e.g. lower than 0.001%). Examples of the nonionicwater-soluble polymer include a partially-saponified polyvinyl alcohol,an oxyalkylene unit-containing polymer, a nitrogen atom-containingpolymer, etc.

The oxyalkylene unit-containing polymer may comprise one, two or morespecies of oxyalkylene unit with 2 to 6 carbon atoms (typically, astructural unit represented by —C_(n)H_(2n)O— wherein n is an integerbetween 2 and 6). The number of carbon atoms in the oxyalkylene unit ispreferably 2 to 3. Examples of such a polymer include a polyethyleneoxide (PEO), a block copolymer of ethylene oxide (EO) and propyleneoxide (PO), a random copolymer of EO and PO, and the like.

The block copolymer of EO and PO can be a diblock copolymer, triblockcopolymer or the like comprising a polyethylene oxide (PEO) block and apolypropylene oxide (PPO) block. Examples of the triblock copolymerinclude a PEO-PPO-PEO triblock copolymer and PPO-PEO-PPO triblockcopolymer. Usually, a PEO-PPO-PEO triblock copolymer is more preferable.

As the PEO-PPO-PEO triblock copolymer, a polymer represented by thefollowing formula (1) can be preferably used:HO-(EO)_(a)—(PO)_(b)-(EO)_(c)—H  (1)

In the general formula (1), EO represents an oxyethylene group(—CH₂CH₂O—), PO represents an oxypropylene group (—CH₂CH(CH₃)O—), andeach of a, b and c is an integer of 1 or higher (typically 2 or higher).

In the general formula (1), the total of a and c is preferably in arange of 2 to 1000, more preferably in a range of 5 to 500, or yet morepreferably in a range of 10 to 200. In the general formula (1), b ispreferably in a range of 2 to 200, more preferably in a range of 5 to100, or yet more preferably in a range of 10 to 50.

In the block or random copolymer of EO and PO, from the standpoint ofthe water solubility and washability, etc., the molar ratio (EO/PO)between EO and PO constituting the copolymer is preferably higher than1, more preferably 2 or higher, or yet more preferably 3 or higher (e.g.5 or higher).

As the nitrogen atom-containing polymer, either a polymer containingnitrogen atoms in the main chain or a polymer having a nitrogen atom inthe side chain functional group (pendant group) can be used.

Examples of the polymer having a nitrogen atom in the main chain includea homopolymer and a copolymer of an N-acylalkyleneimine-based monomer.Specific examples of the N-acylalkyleneimine-based monomer includeN-acetylethyleneimine, N-propionylethyleneimine, N-caproylethyleneimine,N-benzoylethyleneimine, N-acetylpropyleneimine, N-butyrylethyleneimine,etc. The homopolymer of N-acylalkyleneimine-based monomer includepoly(N-acetylethyleneimine), poly(N-propionylethyleneimine),poly(N-caproylethyleneimine), poly(N-benzoylethyleneimine),poly(N-acetylpropyleneimine), poly(N-butyrylethyleneimine), etc.Examples of the copolymer of the N-acylalkyleneimine-based monomerinclude a copolymer of two or more species of N-acylalkyleneimine-basedmonomer and a copolymer of one, two or more species ofN-acylalkyleneimine-based monomer and another monomer.

Unless otherwise indicated, the copolymer in this specificationcomprehensively means various copolymers such as random copolymer,alternating copolymer, block copolymer, graft copolymer, etc.

Examples of a polymer having a nitrogen atom in a pendant group includea polymer comprising an N-(meth)acryloyl monomeric unit, a polymercomprising an N-vinyl monomeric unit, etc. The term “(meth)acryloyl”herein comprehensively refers to acryloyl and methacryloyl.

Examples of the N-(meth)acryloyl monomeric unit-containing polymerinclude a homopolymer of an N-(meth)acryloyl-based monomer and acopolymer thereof (typically a copolymer in which the copolymerizationratio of N-(meth)acryloyl-based monomer exceeds 50% by mass). Examplesof the N-(meth)acryloyl-based monomer include an open-chain amide havingan N-(meth)acryloyl group and a cyclic amide having an N-(meth)acryloylgroup.

Examples of an open-chain amide having an N-(meth)acryloyl groupinclude: (meth)acrylamide; N-alkyl(meth)acrylamides such asN-methyl(meth)acrylamide, N-ethyl(meth)acrylamide,N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide,N-n-butyl(meth)acrylamide, etc.; N,N-dialkyl(meth)acrylamides such asN,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide,N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide,N,N-di(n-butyl)(meth)acrylamide, etc.; and the like. Examples of apolymer comprising a N-(meth)acryloyl group-containing open-chain amideas a monomeric unit include a homopolymer of N-isopropylacrylamide and acopolymer of N-isopropylacrylamide (e.g. a copolymer in which thecopolymerization ratio of N-isopropylacrylamide exceeds 50% by mass).

Examples of the N-(meth)acryloyl group-containing cyclic amide includeN-(meth)acryloylmorpholine, N-(meth)acryloylpyrrolidine, etc. Examplesof a polymer comprising an N-(meth)acryloyl group-containing cyclicamide as a monomeric unit include a homopolymer of N-acryloylmorpholineand a copolymer of N-acryloylmorpholine (e.g. a copolymer in which thecopolymerization ratio of N-acryloylmorpholine exceeds 50% by mass).

Examples of the N-vinyl monomeric unit-containing polymer include ahomopolymer of an N-vinyllactam-based monomer and a copolymer thereof(e.g. a copolymer in which the copolymerization ratio of theN-vinyllactam-based monomer exceeds 50% by weight), a homopolymer of anopen-chain N-vinylamide and a copolymer thereof (e.g. a copolymer inwhich the copolymerization ratio of the open-chain N-vinylamide exceeds50% by weight) and the like.

Specific examples of the N-vinyllactam-based monomer includeN-vinylpyrrolidone (VP), N-vinylpiperidone, N-vinylmorpholinone,N-vinylcaprolactam (VC), N-vinyl-1,3-oxazine-2-one,N-vinyl-3,5-morpholinedione, etc. Specific examples of the N-vinyllactammonomeric unit-containing polymer include a polyvinylpyrrolidone (PVP),polyvinylcaprolactam, random copolymer of VP and VC, random copolymer ofone or each of VP and VC with another vinyl monomer (e.g. acrylicmonomer, vinyl ester-based monomer, etc.), block copolymer and graftcopolymer comprising a polymer segment with one or each of VP and VC(e.g. a graft copolymer obtained by grafting polyvinyl alcohol withpolyvinylpyrrolidone), and the like.

Specific examples of the open-chain N-vinylamide includeN-vinylacetamide, N-vinylpropionic acid amide, N-vinyllactic acid amide,etc.

Other examples of a polymer having a nitrogen atom in a pendant groupinclude a homopolymer and a copolymer of an amino group-containing vinylmonomer (e.g. a monomer having a (meth)acryloyl group) such asaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate,N,N-dimethylaminopropyl (meth)acrylate, etc.

Other examples of the water-soluble polymer that can be contained in thepolishing composition disclosed herein include cellulose derivativessuch as hydroxyethyl cellulose, hydroxyethylmethyl cellulose,hydroxypropylmethyl cellulose, methyl cellulose, ethyl cellulose,ethylhydroxyethyl cellulose, carboxymethyl cellulose, etc.; andpullulan.

The molecular weight of the water-soluble polymer is not particularlylimited. For instance, a water-soluble polymer having a weight averagemolecular weight (Mw) of 200×10⁴ or smaller (typically 1×10⁴ to 200×10⁴,e.g. 1×10⁴ to 150×10⁴) can be used. From the standpoint of betterpreventing formation of aggregates, the use of a water-soluble polymerhaving a Mw of smaller than 100×10⁴ (more preferably 80×10⁴ or smaller,yet more preferably 50×10⁴ or smaller, typically 40×10⁴ or smaller, e.g.30×10⁴ or smaller) is preferable. From the standpoint of the ease offiltering and washing the polishing composition, etc., a water-solublepolymer having a Mw of 25×10⁴ or smaller (typically 20×10⁴ or smaller,more preferably 15×10⁴ or smaller, typically 10×10⁴ or smaller, e.g.5×10⁴ or smaller) can be preferably used. On the other hand, in general,with increasing Mw of water-soluble polymer, the haze reduction effecttends to increase. From such a standpoint, it is usually preferable touse a water-soluble polymer having a Mw of 0.1×10⁴ or larger (typically0.2×10⁴ or larger, e.g. 1×10⁴ or larger).

In the art disclosed herein, the relationship between the weight averagemolecular weight (Mw) and number average molecular weight (Mn) of thewater-soluble polymer is not particularly limited. From the standpointof preventing aggregate formation, etc., for instance, a water-solublepolymer having a molecular weight distribution (Mw/Mn) of 5.0 or lowercan be preferably used. From the standpoint of the consistency ofperformance of the polishing composition, etc., the Mw/Mn of thewater-soluble polymer is preferably 4.0 or lower, more preferably 3.5 orlower, or yet more preferably 3.0 or lower (e.g. 2.5 or lower).

Theoretically, the Mw/Mn is 1.0 or greater. From the standpoint of theavailability of starting materials and ease of synthesis, usually, awater-soluble polymer having an Mw/Mn of 1.05 or higher can bepreferably used.

As the Mw and Mn of a water-soluble polymer, the values based on aqueousgel permeation chromatography (GPC) (aqueous, based on standardpolyethylene oxide) can be used.

<2-2. Water>

As the water contained in the polishing composition according to thesecond aspect, the same kinds as the water described regarding thepolishing composition according to the first aspect can be used.

The polishing composition disclosed herein may further comprise, asnecessary, a water-miscible organic solvent (lower alcohol, lowerketone, etc.). In usual, of the solvent in the polishing composition,preferably 90% by volume or more is water, or more preferably 95% byvolume or more (typically 99 to 100% by volume) is water.

The polishing composition disclosed herein (typically a slurrycomposition) can be preferably made, for instance, in an embodiment inwhich the non-volatile content (NV) is 0.01% by mass to 50% by mass andthe rest is an aqueous solvent (water or a mixture of water and theorganic solvent) or in an embodiment where the rest is an aqueoussolvent and a volatile compound (e.g. ammonia). An embodiment whereinthe NV is 0.05% by mass to 40% by mass is more preferable. Thenon-volatile content (NV) refers to the mass proportion of residueremaining in the polishing composition after drying the polishingcomposition at 105° C. for 24 hours.

<2-3. Abrasive>

The abrasive contained in the polishing composition according to thesecond aspect disclosed herein is the same as the abrasive contained inthe polishing composition according to the first aspect. Thus, detaileddescriptions are omitted.

<2-4. Basic Compound>

The basic compound that can be contained in the polishing compositionaccording to the second aspect disclosed herein is the same as the basiccompound that can be contained in the polishing composition according tothe first aspect. Thus, detailed descriptions are omitted.

<2-5. Surfactant>

The polishing composition according to the second aspect disclosedherein can comprise a surfactant as necessary. Usable surfactants arethe same as in the polishing composition according to the first aspect.Thus, detailed descriptions are omitted.

<2-7. Other Components>

As far as the effects by the present invention are not significantlyhindered, the polishing composition according to the second aspectdisclosed herein may further comprise as necessary known additives, suchas chelating agents, organic acids, organic acid salts, inorganic acids,inorganic acid salts, preservatives, antifungal agents, and so on,usable in polishing compositions (typically, polishing compositions usedfor final polishing of silicon wafers). Additives that can be includedin the polishing composition according to the second aspect are the sameas in the polishing composition according to the first aspect. Thus,detailed descriptions are omitted.

<2-8. Etching Rate and Abrasive Adsorption>

The polishing composition according to the second aspect disclosedherein comprises an abrasive, a water-soluble polymer and water and ischaracterized by having an etching rate of 2.0 nm/min according to theetching rate measurement described earlier and an abrasive adsorption of20% or lower based on the abrasive adsorption measurement describedearlier.

The etching rate can be measured as described below. In particular, forinstance, it can be measured in the same manner as the etching ratemeasurement described later in the working examples.

[Etching Rate Measurement]

(1A) An etching rate measuring reagent LE is prepared, comprising 0.18%by mass of the water-soluble polymer in the polishing composition and1.3% by mass of ammonia with the rest being water.

(2A) A silicon substrate (in a 6 cm long by 3 cm wide by 775 μm thickrectangle) is obtained, from which surface natural oxide film isremoved, and its mass W0 is measured.

(3A) The silicon substrate is immersed in the reagent LE at roomtemperature for 12 hours.

(4A) The silicon substrate is removed from the reagent LE and cleaned atroom temperature for 10 seconds with a cleaning solution formed of NH₃(29%)/H₂O₂ (31%)/ultrapure water=1/1/8 (volume ratio).

(5A) The cleaned silicon substrate is measured for its mass W1.

(6A) From the difference between the W0 and W1 as well as the specificgravity of the silicon substrate, the etching rate (nm/min) isdetermined.

The etching rate of a polishing composition comprising two or morespecies of water-soluble polymer can be determined by carrying out theetching rate measurement, using the two or more species of water-solublepolymer at the same ratio as in the polishing composition.

The abrasive adsorption can be measured as described below. Inparticular, for instance, it can be measured in the same manner as theabrasive adsorption measurement as described later in the workingexamples.

[Measurement of Abrasive Adsorption]

The abrasive adsorption is determined as follows:

(1B) The polishing composition is centrifuged to precipitate theabrasive and the resulting supernatant is subjected to measurement oftotal organic carbon to determine the total amount of organic carbon,C1, in the supernatant.

(2B) A test solution L0 is obtained having the same composition as thatof the polishing composition but without the abrasive and the testsolution L0 is subjected to measurement of total organic carbon todetermine the total amount of organic carbon, C0, in the test solutionL0.

(3B) From the C0 and C1, the abrasive adsorption is determined by thefollowing equation:Abrasive adsorption (%)=[(C0−C1)/C0]×100

The abrasive adsorption being 20% or lower means that most (typicallymore than 80% by mass) of the water-soluble polymer in the polishingcomposition is not adsorbed on the abrasive. The water-soluble polymernot adsorbed on the abrasive (or free polymer hereinafter) can adherequickly to the polishing object surface and thus may be highlyprotective to the surface in comparison with the polymer adsorbed on theabrasive. Accordingly, in polishing with a polishing composition havinga higher free polymer content (a low abrasive adsorption), thewater-soluble polymer in the polishing composition can serve moreeffectively to protect the surface of the polishing object.

On the other hand, the ability of the water-soluble polymer to protectthe polishing object surface may vary also in accordance with thecharacteristics of the water-soluble polymer. The etching rate can serveas an index to evaluate the ability of the water-soluble polymer toprotect the polishing object surface from alkaline corrosion underconditions not influenced by the mechanical force of the abrasive. Alower etching rate tends to indicate a greater ability to inhibitadsorption of the water-soluble polymer to the polishing object surfaceto causes the basic compound, etc., to chemically etch the surface, thatis, a greater ability to protect the polishing object surface. Thepolishing composition disclosed herein comprises a surface-protectivewater-soluble polymer yielding an etching rate of a prescribed value orlower. In other words, most of the water-soluble polymer is present asfree polymer in the liquid phase and some is adsorbed to the abrasive tosuitably exhibit the effect to reduce the haze in the polishing objectsurface. Because of the low abrasive adsorption, aggregates of theabrasive and water-soluble polymer are unlikely to be formed. This isthought to advantageously contribute to reduce the number of LPD andincrease the ease of filtration of the polishing compound.

From the standpoint of the ability to protect the surface (and furtherof the haze reduction effect), the etching rate is preferably lower than2.0 nm/min, more preferably 1.8 nm/min or lower, or yet more preferably1.5 nm/min or lower. From the standpoint of obtaining greater hazereduction effect, the polishing composition disclosed herein can also bepreferably made in an embodiment wherein the etching rate is 1.2 nm/minor lower (or even lower than 1.0 nm/min). The lower limit of etchingrate is not particularly limited. From the standpoint of the polishingefficiency, it is usually preferably 0.3 nm/min or higher, or morepreferably 0.5 nm/min or higher.

From the standpoint of combining the haze reduction effect and LPD countreduction effect at a high level, the abrasive adsorption is preferably20% or lower (typically lower than 20%), more preferably 15% or lower,or even more preferably 10% or lower. From the standpoint of obtaining asurface of higher quality, the polishing composition disclosed hereincan also be preferably made in an embodiment wherein the abrasiveadsorption is 5% or lower (more preferably 3% or lower, or evenessentially 0%).

The type and amount (concentration) of water-soluble polymer in thepolishing composition according to the second aspect disclosed hereincan be selected so as to satisfy the aforementioned etching rate andabrasive adsorption in accordance with the type (material, size, shape)and concentration of the abrasive being used, pH of the polishingcomposition and so on.

For the water-soluble polymer, among known water-soluble polymers (e.g.the water-soluble polymers exemplified earlier), solely one species or acombination of two or more species can be used. When two or more speciesof water-soluble polymer are used in combination, they can be used at aratio that satisfies the etching rate and abrasive adsorption.

The polishing composition according to the second aspect disclosedherein can be preferably made in, but not particularly limited to, anembodiment comprising solely one species of water-soluble polymer(typically an embodiment wherein solely one species of water-solublepolymer having a Mw larger than 1×10⁴ is present among other componentsin the polishing composition). Because of its simple composition, such apolishing composition can be advantageous in terms of reducing rawmaterial costs, minimizing the manufacturing facility, increasing theconsistency of quality, facilitating the quality control, and so on. Apreferable example of water-soluble polymers that can be used in thepolishing composition in such an embodiment is a polyvinyl alcoholhaving a degree of saponification of lower than 95% by mole (morepreferably 90% by mole or lower, even more preferably 85% by mole orlower, typically 80% by mole or lower). Such a polyvinyl alcohol used asthe water-soluble polymer in the polishing composition has a degree ofsaponification of preferably 60% by mole or higher, or more preferably65% by mole or higher (e.g. 70% by mole or higher).

In such an embodiment comprising solely one species of water-solublepolymer, from the standpoint of the ease of filtration, washability,etc., the water-soluble polymer (e.g. a polyvinyl alcohol having adegree of saponification of lower than 95% by mole) has a Mw ofpreferably 25×10⁴ or smaller (more preferably 20×10⁴ or smaller, yetmore preferably 15×10⁴ or smaller, typically 10×10⁴ or smaller, e.g.5×10⁴ or smaller). From the standpoint of haze reduction, thewater-soluble polymer preferably has a Mw of 1×10⁴ or larger.

In the polishing composition according to the second aspect disclosedherein, a water-soluble polymer having a Mw of 3×10⁴ or smaller can bepreferably used. The Mw of the water-soluble polymer can be 2×10⁴ orsmaller, 1×10⁴ or smaller, or even 0.5×10⁴ or smaller (e.g. 0.4×10⁴ orsmaller). The Mw of the water-soluble polymer is typically 1×10³ orlarger or usually preferably 0.2×10⁴ or larger. For instance, this Mwranges can be preferably applied to a water-soluble polymer comprisingat least a vinyl alcohol unit.

From the standpoint of preventing formation of aggregates, etc., thewater-soluble polymer's Mw/Mn is suitably, but not particularly limitedto, 5.0 or less (typically 1.05 or greater, but 5.0 or less), preferably4.0 or less, more preferably 3.5 or less, or even more preferably 3.0 orless (e.g. 2.5 or less).

For selecting a water-soluble polymer for use as a component in thepolishing composition according to the second aspect disclosed herein,for instance, the repeat units and their proportions of thewater-soluble polymer can be taken into account. This allows forefficient selection of a water-soluble polymer that satisfies desirableetching rate and abrasive adsorption. More specifically, as thewater-soluble polymer in the polishing composition according to thesecond aspect disclosed herein, a water-soluble polymer having repeatunits A and B with a mole ratio in a range described earlier can bepreferably used. A polishing composition comprising such a water-solublepolymer has suitably-balanced water solubility, adsorption to theabrasive (typically a silica abrasive) and to a polishing object to bepolished (e.g. a silicon substrate), and is likely to satisfy preferableetching rate and abrasive adsorption.

The water-soluble polymer may comprise solely one species of repeat unitA or two or more such species in combination. Specific examples of therepeat unit A include those listed in Table 1 above.

The water-soluble polymer may comprise solely one species of repeat unitB or a combination of two or more such species. Specific examples of therepeat unit B include those listed in Table 2 above.

When the polishing composition disclosed herein comprises a cellulosederivative, its amount used is preferably at most 40% by mass of thetotal water-soluble polymer in the polishing composition, morepreferably 25% by mass or less, or yet more preferably 10% by mass orless (typically 5% by mass or less). This can bring about greaterinhibition of contamination and aggregation caused by the use of anaturally-derived cellulose derivative. The polishing compositiondisclosed herein can be preferably made, for instance, in an embodimentessentially free of a cellulose derivative as the water-soluble polymer.

Although not particularly limited, the water-soluble polymer content canbe, for instance, 0.01 part by mass or higher to 100 parts by mass ofthe abrasive. From the standpoint of increasing the polished surfacesmoothness (e.g. reduction of haze and defects), the water-solublepolymer content relative to 100 parts by mass of the abrasive issuitably 0.05 part by mass or higher, preferably 0.1 part by mass orhigher, or more preferably 0.5 part by mass or higher (e.g. 1 part bymass or higher). From the standpoint of the polishing rate andwashability, etc., the water-soluble polymer content relative to 100parts by mass of the abrasive can be, for instance, 40 parts by mass orless, usually suitably 20 parts by mass or less, preferably 15 parts bymass or less, or more preferably 10 parts by mass or less.

The art disclosed herein can be implemented in an embodiment of thepolishing composition that comprises a water-soluble polymer Q andsatisfies the following conditions: having a Mw of 1×10⁴ or larger;comprising a hydroxyl group-containing repeat unit h; and having ahydroxyl group content in a range from 4 mmol/g up to 21 mmol/g. Thewater-soluble polymer Q can be any water-soluble polymer describedearlier. A polishing composition comprising such a water-soluble polymerQ is preferably supplied to a polishing object with the hydroxyl groupcontent of the water-soluble polymer being maintained in a range from 4mmol/g up to 21 mmol/g when used for polishing the polishing object. Therepeat unit h can be, for instance, a vinyl alcohol unit.

<2-9. Applications>

Applications of the polishing composition according to the second aspectdisclosed herein are the same as the polishing composition according tothe first aspect. Thus, detailed descriptions are omitted.

<2-10. Polishing Liquid and Concentrate>

The polishing liquid and concentrate of the polishing compositionaccording to the second aspect disclosed herein are the same as thepolishing composition according to the first aspect. Thus, detaileddescriptions are omitted.

<2-11. Preparation of Polishing Composition>

Preparation of the polishing composition according to the second aspectdisclosed herein is the same as the polishing composition according tothe first aspect. Thus, detailed descriptions are omitted.

<2-12. Polishing>

The polishing composition according to the second aspect disclosedherein can be used for polishing in the same manner as the polishingcomposition according to the first aspect. Thus, detailed descriptionsare omitted.

<2-13. Cleaning>

A polishing object polished with the polishing composition according tothe second aspect disclosed herein can be cleaned in the same manner aswith the polishing composition according to the first aspect. Thus,detailed descriptions are omitted.

<<3. Polishing Composition Production Method According to First Aspect>>

The polishing composition production method according to the firstaspect disclosed herein is a method for producing a polishingcomposition, using an abrasive, a basic compound, a water-solublepolymer H having an alkaline-hydrolytic functional group, and water,with the method comprising: a step of obtaining an agent A comprising atleast the basic compound;

a step of obtaining an agent B comprising at least the water-solublepolymer H; and a step of mixing a first composition comprising at leastthe agent A and a second composition comprising at least the agent B toprepare a mixture that comprises the abrasive, the basic compound, thewater-soluble polymer H and water at a concentration of the basiccompound of 0.1 mol/L or lower. Described in detail below is thepolishing composition production method according to the first aspect.

<3-1. Water-Soluble Polymer H>

The polishing composition production method according to the firstaspect disclosed herein is preferably applied to production of apolishing composition comprising a water-soluble polymer (water-solublepolymer H) having an alkaline-hydrolytic functional group (or a“hydrolytic group” hereinafter). The water-soluble polymer H typicallyhas a ratio of the number of moles (molar ratio) of hydrolyticgroup-containing repeat units to the number of moles of all repeat unitsin the molecular structure exceeds 2%. In producing such a polishingcomposition, a great effect can be obtained by the use of the methoddisclosed herein. An object (product) to which the method disclosedherein is preferably applied is a polishing composition that comprises awater-soluble polymer H having a molar ratio of a hydrolytic group of 5%or higher.

The polishing composition production method disclosed herein can bepreferably implemented in an embodiment using a water-soluble polymer Hhaving an ester group as the alkaline-hydrolytic functional group.Examples of the ester group-containing water-soluble polymer H includehomopolymers and copolymers of a vinyl carboxylate and a (meth)acrylicacid ester as well as modification products (e.g. saponificationproducts) of these, and the like. Specific examples of the vinylcarboxylate include vinyl acetate, vinyl propionate, vinyl lactate, etc.Specific examples of the (meth)acrylic acid ester include methylacrylate, 2-hydroxyethyl acrylate, methyl methacrylate, etc. Uponhydrolysis of such ester group-containing water-soluble polymers H, forexample, polyvinyl carboxylate is converted to a polymer having a polyolmain chain while poly(meth)acrylic acid ester is converted to apoly(meth)acrylic acid.

Other examples of the water-soluble polymer H include apoly(meth)acrylamide having an amide group as the alkaline-hydrolyticfunctional group, an alkoxysilyl group-containing polyalkoxysilanederivative, a polyacetal, etc. Upon hydrolysis, these are converted topolycarboxylic acid, polysilanol, polyaldehyde, etc., respectively.

The copolymer in this specification comprehensively refers to varioustypes of copolymer such as random copolymer, alternating copolymer,block copolymer, graft copolymer, etc. The term “(meth)acrylic acid”comprehensively refers to acrylic acid and methacrylic acid while theterm “(meth)acryloyl” comprehensively refers to acryl and methacryl.

In the art disclosed herein, a preferable example of the water-solublepolymer H comprises a vinyl carboxylate unit in its molecular structure.For instance, a preferable water-soluble polymer H includes a structuralmoiety equivalent to a structure resulting from polymerization of thevinyl group in the vinyl carboxylate represented by the formulaRCOOCH═CH₂. Herein, R is a primary organic group and preferably ahydrocarbon group having 1 to 6 carbon atoms. In particular, such astructural moiety is represented by the formula —CH₂—CH(OCOR)—. Typicalexamples of the vinyl carboxylate unit include vinyl acetate unit(structural moiety represented by the formula —CH₂—CH(OCOCH₃)—)resulting from polymerization of the vinyl group in vinyl acetate(CH₃COOCH═CH₂).

The water-soluble polymer H comprises a total of more than 2% by mole ofone, two or more species of repeat unit (e.g. vinyl carboxylate unit)having a hydrolytic group, more preferably 5% by mole or greater (at amolar ratio of 5% or higher), or yet more preferably 10% by mole orgreater. From the standpoint of obtaining greater application effect ofthe production method disclosed herein, a water-soluble polymer having amolar ratio of hydrolytic group-containing repeat unit of 15% or higher(or even 20% or higher) can be preferably used.

The upper limit of molar ratio of the hydrolytic group-containing repeatunit in the water-soluble polymer H is not particularly limited. Fromthe standpoint of the water solubility of the water-soluble polymer H,it is typically 80% or lower, usually preferably 60% or lower, morepreferably 50% or lower, or yet more preferably 40% or lower (e.g. 30%or lower).

A preferable example of the water-soluble polymer H is a saponificationproduct of a vinyl acetate homopolymer or copolymer. A particularlypreferable water-soluble polymer H is the saponification product of avinyl acetate homopolymer. Such a water-soluble polymer H can be thoughtas a partially-saponified polyvinyl alcohol comprising vinyl acetateunits (—CH₂—CH(OCOCH₃)—) and vinyl alcohol units (—CH₂—CH(OH)—) formedby saponification of the vinyl acetate units at a ratio (molar ratio)corresponding to the degree of saponification. Such apartially-saponified polyvinyl alcohol may have a degree ofsaponification of typically higher than 2% by mole, usually 5% by moleor higher, preferably 10% by mole or higher, or more preferably 15% bymole or higher (e.g. 20% by mole or higher). The degree ofsaponification of the partially-saponified polyvinyl alcohol istypically 80% by mole or lower, usually 60% by mole or lower, preferably50% by mole or lower, or more preferably 40% by mole or lower (e.g. 30%by mole or lower).

The molecular weight of the water-soluble polymer is not particularlylimited. For instance, a water-soluble polymer having a weight averagemolecular weight (Mw) of 200×10⁴ or smaller (typically 1×10⁴ to 200×10⁴,e.g. 1×10⁴ to 150×10⁴) can be used. From the standpoint of betterpreventing formation of aggregates, the use of a water-soluble polymerhaving a Mw of smaller than 100×10⁴ (more preferably 80×10⁴ or smaller,yet more preferably 50×10⁴ or smaller, typically 40×10⁴ or smaller, e.g.30×10⁴ or smaller) is preferable. From the standpoint of the ease offiltering and washing the resulting polishing composition, etc., awater-soluble polymer having a Mw of 25×10⁴ or smaller (typically 20×10⁴or smaller, more preferably 15×10⁴ or smaller, typically 10×10⁴ orsmaller, e.g. 5×10⁴ or smaller) can be preferably used. On the otherhand, in general, with increasing Mw of water-soluble polymer, the hazereduction effect tends to increase. From such a standpoint, it isusually preferable to use a water-soluble polymer having a Mw of 1×10⁴or larger.

In the art disclosed herein, the relationship between the weight averagemolecular weight (Mw) and number average molecular weight (Mn) of thewater-soluble polymer is not particularly limited. From the standpointof preventing formation of aggregates, etc., for instance, a specieshaving a molecular weight distribution (Mw/Mn) of 5.0 or less can bepreferably used. From the standpoint of the performance stability of thepolishing composition, the water-soluble polymer's Mw/Mn is preferably4.0 or less, more preferably 3.5 or less, or yet more preferably 3.0 orless (e.g. 2.5 or less). Theoretically, the Mw/Mn is 1.0 or greater.From the standpoint of the availability of starting materials and theease of synthesis, in usual, a water-soluble polymer having an Mw/Mn of1.05 or greater can be preferably used.

As the Mw and Mn of a water-soluble polymer, the values (aqueous, basedon standard polyethylene oxide) based on aqueous gel permeationchromatography (GPC) can be used.

The water-soluble polymer is preferably nonionic. In other words, awater-soluble polymer H essentially free of anionic and cationic repeatunits is preferable. Herein, being essentially free of anionic andcationic repeat units means that the molar ratio of these repeat unitsis lower than 0.02% (e.g. lower than 0.001%). According to the polishingcomposition that comprises a nonionic water-soluble polymer H, it ispossible to obtain greater effect to reduce the haze value and thenumber of LPD in the polished surface. The water-soluble polymer H beingnonionic is preferable also from the standpoint of reducing aggregatesand increasing the washability, etc.

<3-2. Abrasive, Basic Compound, Water>

The abrasive, the basic compound and water usable in the polishingcomposition production method according to the first aspect disclosedherein are the same as in the polishing composition according to thefirst aspect disclosed herein. Thus, detailed descriptions are omitted.

<3-3. Production of Polishing Composition>

The polishing composition production method according to the firstaspect disclosed herein is implemented, using an abrasive, a basiccompound, a water-soluble polymer H and water as described earlier. Theproduction method is characterized by comprising a step of obtaining anagent A comprising at least the basic compound, a step of obtaining anagent B comprising at least the water-soluble polymer H, and furthercomprising a step of mixing a first composition comprising at least theagent A and a second composition comprising at least the agent B toprepare a mixture that satisfies one or each of the following (A) and(B):

(A) comprising the abrasive, the basic compound, the water-solublepolymer and water; and having a concentration of the basic compound of0.1 mol/L or lower.

(B) comprising the abrasive, the basic compound, the water-solublepolymer H and water; and having a concentration of the abrasive of lowerthan 3% by mass.

By applying the production method featuring the characteristicsdescribed above, a polishing composition produced by the art disclosedherein has excellent temporal stability of polishing performance despiteof being a basic polishing composition. Accordingly, there are noparticular limitations imposed on the time (storage time) from thepreparation of the mixture that satisfies one or each of the (A) and (B)above to the actual use of a polishing composition comprising themixture. This is preferable from the standpoint of the high flexibilityof the polishing composition's storage process and use process (e.g. aprocess of polishing a polishing object with the polishing compositionand a production process of a polished article involving the polishing).The time from the preparation of the mixture satisfying one or each ofthe (A) and (B) to the actual use of a polishing composition comprisingthe mixture can be, for instance, more than 12 hours, more than 24hours, or even more than 48 hours (e.g. more than 48 hours up to threemonths). Needless to say, this does not hinder the use of the polishingcomposition in shorter time than the above. For instance, the time fromproduction of the polishing composition to the actual use can be threehours or less, one hour or less, or even 30 minutes or less.

Typical embodiments of the polishing composition production methodaccording to the first aspect disclosed herein is described with respectto an example of producing a polishing composition, using silica grainsas the abrasive, ammonia as the basic compound and apartially-saponified polyvinyl alcohol (degree of saponification 73% bymole) as the water-soluble polymer H, but the embodiments and productsof the present invention are not limited by these.

First Embodiment

In this embodiment, a polishing composition is produced, using apolishing composition preparation kit in which the following agents Aand B are separately stored:

Agent A: an abrasive dispersion comprising an abrasive, a basic compoundand water (a basic abrasive dispersion with 5 to 25% by mass abrasivecontent at a basic compound concentration of 0.0001 mol/L to 1 mol/L)

Agent B: an aqueous solution of a water-soluble polymer H (an aqueouspolymer solution with 0.02 to 50% by mass polymer content at about pH 6)

Specifically, for instance, water is added to the agent A (abrasivedispersion C) to prepare a first composition that satisfies at leasteither the abrasive content being less than 3% by mass or the basiccompound concentration being 0.1 mol/L or lower. Subsequently, the agentB is added to the first composition (dilute agent A in this embodiment)and mixed to obtain a polishing composition.

In this embodiment, after the agent B is added to the first compositionand mixed, water may be further added as necessary to adjust theabrasive concentration of the polishing composition. Alternatively,after the agent B is added to the first composition and mixed, a basiccompound may be further added as necessary to adjust the pH of thepolishing composition.

According to this embodiment, while using a water-soluble polymer H, abasic polishing composition can be produced with excellent stability ofpolishing performance, by means of adding an aqueous water-solublepolymer H solution (agent B) to the first composition that satisfies atleast either the abrasive content being less than 3% by mass or thebasic compound concentration being 0.1 mol/L or lower.

One reason for acquisition of such an effect may have to do with theco-presence of the abrasive and the water-soluble polymer H in theabrasive dispersion having an abrasive concentration of lower than 3% bymass achieved simultaneously with or before (in this embodiment,simultaneously with) achieving the co-presence of the basic compound andthe water-soluble polymer H. Another reason for acquisition of theeffect may have to do with the co-presence of the basic compound and thewater-soluble polymer H achieved simultaneously with or before (in thisembodiment, simultaneously with) obtaining a basic compoundconcentration of 0.1 mol/L or lower.

Because the agent A (abrasive dispersion C) used in this embodiment isin a state where the abrasive and the basic compound are co-present, theabrasive has increased electrostatic repulsion due to the basic compoundand thereby exhibits high dispersion stability. Thus, when mixed withthe water-soluble polymer, local aggregation of the abrasive can behighly prevented.

The agent B used in this embodiment is prepared as an aqueous solutionin which the water-soluble polymer H has been dissolved in water inadvance. Accordingly, when mixed with the first composition, localaggregation of the abrasive can be highly prevented. This is preferablefrom the standpoint of increasing the ease of filtration of a polishingcomposition produced according to the present embodiment or reducingdefects in the polished surface.

The agent A (abrasive dispersion C) in this embodiment is advantageousfrom the standpoint of the convenience and reduction of costs ofproduction, distribution, storage, etc., because it is in a concentratedform (a form at a high abrasive concentration) when compared with apolishing composition to be produced. The abrasive content in the agentA in such a concentrated form can be, for instance, 50% by mass or less.From the standpoint of the stability (e.g. the abrasive's dispersionstability) and ease of filtration of a polishing composition producedwith the agent A, in usual, the abrasive content is preferably 45% bymass or less, or more preferably 40% by mass or less. In a preferableembodiment, the abrasive content can be 30% by mass or less, or even 20%by mass or less (e.g. 15% by mass or less). From the standpoint of theconvenience and reduction of costs of production, distribution, storage,etc., the abrasive content can be, for instance, 0.5% by mass orgreater, preferably 1% by mass or greater, or more preferably 3% by massor greater.

The basic compound content in the agent A is preferably 0.001% by massor greater, more preferably 0.005% by mass or greater, or yet morepreferably 0.01% by mass or greater. With increasing basic compoundcontent, local aggregation tends to be inhibited to a greater extentwhen the agent A is diluted or mixed with the agent B. The basiccompound content in the agent A is preferably 10% by mass or less, morepreferably 5% by mass or less, or yet more preferably 3% by mass orless. With decreasing basic compound content, it becomes easier toadjust the basic compound content in the polishing composition.

The agent A has a pH of preferably 9 or higher, or more preferably 9.5or higher. With increasing pH, local aggregation tends to be inhibitedto a greater extent when the agent A is diluted or mixed with the agentB. In general, at a higher pH, the rate of hydrolysis of thewater-soluble polymer H increases. Thus, it may be more meaningful toapply the production method disclosed herein. The agent A has a pH ofpreferably 12 or lower, more preferably 11.5 or lower, or yet morepreferably 10.5 or lower. When the agent A's pH is set low, a smalleramount of the basic compound is required to prepare the agent A, wherebyit becomes easier to adjust the basic compound content in the polishingcomposition. For instance, when the abrasive is silicon particles, thepH being not exceedingly high is advantageous also from the standpointof inhibiting dissolution of the silica. The agent A's pH can beadjusted by the amount (concentration) of the basic compound added andso on.

The water-soluble polymer H content (concentration) in the agent B ispreferably 0.02% by mass or greater, more preferably 0.05% by mass orgreater, or yet more preferably 0.1% by mass or greater. With increasingwater-soluble polymer H content, it becomes easier to adjust thewater-soluble polymer H content in the polishing composition. Thewater-soluble polymer H content in the agent B is preferably 50% by massor less, and can be, for instance, 20% by mass or less. With decreasingwater-soluble polymer H content, local aggregation of the abrasive tendsto be inhibited to a greater extent when the agent B is added to thefirst composition (in this embodiment, the diluted agent A).

From the standpoint of inhibiting hydrolysis of the water-solublepolymer H, the agent B is preferably formulated to a near-neutral pH ingeneral. The agent B's pH is usually preferably 4 or higher, but lowerthan 9, or more preferably 5.5 to 7.5. The art disclosed herein can beimplemented, for instance, in an embodiment wherein the agent B's pH isaround 6 (e.g. 6±0.3). In a preferable embodiment, the agent B can beprepared in a composition essentially free of a basic compound (e.g. acomposition consisting of a water-soluble polymer H and water).

In this embodiment, the agent A comprising the abrasive and basiccompound is diluted to prepare the first composition and the agent B isthen added to the first composition. The agent A can be diluted by afactor that yields at least either an abrasive concentration of lowerthan 3% by mass or a basic compound concentration of 0.1 mol/L or lowerin the first composition. The dilution factor can be, for instance,about 2 to 200 by volume, or is usually suitably about 5 to 100. Thedilution factor according to a preferable embodiment is 10 to 80. Forinstance, it is preferably diluted by a factor of 15 to 40.

Preferable abrasive concentrations in the first composition (dilutedagent A) may also vary in accordance with the abrasive concentration ofthe polishing composition to be produced. In usual, the abrasiveconcentration is preferably 2% by mass or lower, or more preferably 1%by mass or lower (e.g. 0.7% by mass or lower). In a preferableembodiment, the abrasive concentration of the first composition can beabout equal to or slightly higher than the abrasive concentration of thepolishing composition to be produced. For instance, the concentrationcan be higher by 1 to 10% by mass than the abrasive concentration of thepolishing composition being produced.

Preferable basic compound concentrations of the first composition(diluted agent A) may also vary depending on the basic compoundconcentration of the polishing composition being produced. Usually, itis preferably 0.1 mol/L or lower, more preferably 0.05 mol/L or lower,or yet more preferably 0.02 mol/L or lower. In a preferable embodiment,the basic compound concentration of the first composition can be aboutequal to or slightly higher than the basic compound concentration of thepolishing composition being produced. For example, the concentration(mol/L) can be higher by about 1 to 10% than the basic compoundconcentration (mol/L) of the polishing composition being produced.

The agents A and B are preferably mixed in an embodiment where the agentB is added to the first composition (diluted agent A) as describedearlier. According to such a mixing method, local aggregation of theabrasive can be prevented to a greater extent as compared with, forinstance, a mixing method where the first composition is added to theagent B. When the abrasive is silica grains (e.g. colloidal silicagrains), as described above, it is particularly meaningful to employ themixing method where the agent B is added to the first composition.

The agent B is added to the first composition at a rate (supply rate) ofpreferably, to a liter (1 L) of the first composition, 500 mL of agent Bper minute or lower, more preferably 100 mL/min or lower, or yet morepreferably 50 mL/min or lower. By decreasing the supply rate, localaggregation of the abrasive can be inhibited to a greater extent.

For preparing the agents A and B, diluting the agent A to prepare thefirst composition, or adding the agent B to the first composition andmixing, etc., the apparatus used is not particularly limited. Forinstance, a known mixer can be used, such as a propeller mixer,ultrasonic disperser, homomixer and the like.

In a preferable embodiment, the agent B can be filtered before mixedwith the first composition. The filtration method is not particularlylimited. For instance, can be suitably employed natural filtrationcarried out at normal pressure or a known filtration method such assuction filtration, pressure filtration, centrifugal filtration, etc.

In this embodiment, until the agent B is added to the first composition(diluted agent A), the basic compound in the agent A and thewater-soluble polymer H in the agent B are not allowed to be co-present.Thus, the time from the dilution of the agent A (i.e. from thepreparation of the first composition) up to the addition of the agent Bis not particularly limited. This is preferable from the standpoint ofthe high flexibility of the production process of the polishingcomposition. The time from the preparation of the first composition tothe addition of the agent B can be, for instance, more than 12 hours,more than 24 hours, or even more than 48 hours (e.g. more than 48 hoursup to three months). Needless to say, the agent B may be added to thefirst composition within a time period shorter than these. For instance,the time from the preparation of the first composition through theaddition of the agent B can be three hours or less, one hour or less, oreven 30 minutes or less.

In a modified example of the first embodiment, for instance, water isadded to the agent B to prepare a second composition (diluted agent B),and the second composition is added to the agent A and mixed to preparea mixture that satisfies one or each of the abrasive content being lessthan 3% by mass and the basic compound concentration being 0.1 mol/L orlower. Alternatively, the agents A and B are mixed with water fordilution at the same time to prepare a mixture that satisfies one oreach of the abrasive content being less than 3% by mass and the basiccompound concentration being 0.1 mol/L or lower. The kit according tothe first embodiment may be formulated to comprise, as the agent A, anabrasive dispersion in a pre-diluted form (i.e. in a form that satisfiesone or each of the abrasive content being less than 3% by mass and thebasic compound concentration being 0.1 mol/L or lower) so that the agentB can be added to the agent A to prepare a polishing composition. Apolishing composition with excellent performance stability can beproduced according to these modification examples as well.

Second Embodiment

In this embodiment, a polishing composition is produced, using apolishing composition preparation kit in which the following agents A, Band C are stored separately:

Agent A: an aqueous solution of a basic composition (an aqueous solutionat a basic composition concentration of 0.0001 mol/L to 1 mol/L)

Agent B: an aqueous solution of a water-soluble polymer H (an aqueouspolymer solution at a polymer concentration of 0.02 to 50% by mass atabout pH 6)

Agent C: a dispersion comprising an abrasive and water (an abrasivedispersion with 5 to 25% by mass abrasive content)

In particular, for instance, water is added to the agent C at a dilutionto yield an abrasive content of less than 3% by mass. The agent B isadded to the diluted agent C and mixed. Subsequently, the agent A isfurther added and mixed to obtain a polishing composition.

In this embodiment, first, to the abrasive dispersion (diluted agent C)with an abrasive content of less than 3% by mass but free of a basiccompound, the aqueous water-soluble polymer H solution (agent B) isadded. This brings about a state in which the abrasive and thewater-soluble polymer H are co-present in the abrasive dispersion withless than 3% by mass abrasive content. Subsequently, by adding andmixing the agent A, while using the water-soluble polymer H, a basicpolishing composition can be produced with excellent stability ofpolishing performance.

In this embodiment, until the agent A is added to the mixture of thediluted agent C and agent B, the basic compound in the agent A and thewater-soluble polymer H in the agent H are not allowed to be co-present.Thus, the time from the preparation of the mixture of the diluted agentC and agent B up to the addition of the agent A is not particularlylimited. This is preferable from the standpoint of the high flexibilityof the production process of the polishing composition. The time fromthe preparation of the mixture of the diluted agent C and agent B to theaddition of the agent A can be, for instance, more than 12 hours, morethan 24 hours, or even more than 48 hours (e.g. more than 48 hours up tothree months). Needless to say, the agent A may be added to the mixturewithin a time period shorter than these. For instance, the time from thepreparation of the mixture of the diluted agent C and agent B to theaddition of the agent A can be three hours or less, one hour or less, oreven 30 minutes or less.

In a modified example of the second embodiment, for instance, somediluted agent B is added and mixed into the agent C to prepare a mixturewhere the abrasive and water-soluble polymer H are co-present at anabrasive concentration of lower than 3% by mass, and then the agent A isadded to the mixture. According to the modified example, adding thediluted agent B to the agent C and mixing them bring about a state inwhich the abrasive and the water-soluble polymer H are co-present in theabrasive dispersion at an abrasive concentration of lower than 3% bymass. By adding the agent A to the mixture, while using thewater-soluble polymer H, a basic polishing composition can be producedwith excellent stability of polishing performance. Alternatively, afterthe agents B and C are mixed with water for dilution to prepare amixture comprising the abrasive and water-soluble polymer H together atan abrasive concentration of lower than 3% by mass, the agent A may beadded to the mixture.

In yet another modification example of the present embodiment, after theagents A and C are mixed with water for dilution to prepare a firstcomposition having less than 3% by mass abrasive content, the agent B isadded to the first composition and mixed to obtain a polishingcomposition. According to this modification example, the co-presence ofthe abrasive and the water-soluble polymer H in the abrasive dispersionbelow 3% by mass abrasive content is achieved simultaneously as theco-presence of the basic compound and the water-soluble polymer H. Bythis means, while using the water-soluble polymer H, a basic polishingcomposition can be produced with excellent stability of polishingperformance.

In yet another modified example of the present embodiment, after theagents A and C are mixed with water for dilution to prepare a firstcomposition at a basic compound concentration of 0.1 mol/L or lower, andthe agent B is added to the first composition and mixed to obtain apolishing composition. According to this modification example, theco-presence of the basic compound and the water-soluble polymer H isachieved simultaneously as the state at a basic compound concentrationof 0.1 mol/L or lower. By this means, while using the water-solublepolymer H, a basic polishing composition can be produced with excellentstability of polishing performance.

Third Embodiment

In this embodiment, a polishing composition is produced, using apolishing composition preparation kit in which the following agents Aand B are stored separately:

Agent A: an aqueous solution of a basic composition (an aqueous solutionat a basic composition concentration of 0.0001 mol/L to 1 mol/L)

Agent B: an aqueous dispersion comprising an abrasive and awater-soluble polymer H (polymer content 0.02 to 50% by mass, abrasivecontent 5 to 25% by mass at about pH 7).

In particular, for instance, water is added to the agent B at a dilutionto yield an abrasive content of less than 3% by mass. The agent A isadded to the diluted agent B and mixed.

In this embodiment, first, the aqueous dispersion (agent B) comprisingthe abrasive and water-soluble polymer H is diluted to an abrasivecontent of less than 3% by mass. This brings about a state in which theabrasive and the water-soluble polymer H are co-present in the abrasivedispersion with less than 3% by mass abrasive content. Subsequently, theaqueous basic compound solution (agent A) is added. Accordingly, theco-presence of the abrasive and the water-soluble polymer H in theabrasive dispersion below 3% by mass abrasive content can be achievedbefore achieving the co-presence of the basic compound and thewater-soluble polymer H. By this means, while using the water-solublepolymer H, a basic polishing composition can be produced with excellentstability of polishing performance.

<3-4. Polishing Composition>

In typical, the polishing composition production method according to thefirst aspect disclosed herein can be preferably applied to production ofa polishing composition (typically a slurry composition) having anon-volatile content (NV) of 5% by mass or less. More preferably, it isapplied to production of a polishing composition having an NV of 0.05%by mass to 3% by mass (e.g. 0.05 to 2% by mass). The non-volatilecontent (NV) refers to the proportion of the mass of residue remainingafter a polishing composition is allowed to dry at 105° C. for 24 hoursin the polishing composition. In typical, the method disclosed hereincan be preferably applied to production of a polishing compositionhaving an abrasive content of less than 3% by mass. A preferable targetproduct is a polishing composition having an abrasive content of 0.05 to2% by mass (more preferably 0.05 to 1% by mass).

The water-soluble polymer H content in the polishing compositionproduced by the method disclosed herein is not particularly limited. Forinstance, it can be 1×10⁻⁴% by mass or greater. From the standpoint ofhaze reduction, etc., the polymer H content is preferably 5×10⁻⁴% bymass or greater, or more preferably 1×10⁻³% by mass or greater, forexample, 2×10⁻³% by mass or greater. From the standpoint of thepolishing rate, etc., the polymer H content is preferably 0.5% by massor less, or more preferably 0.2% by mass or less (e.g. 0.1% by mass orless).

The water-soluble polymer H content can be, but not particularly limitedto, for instance, 0.01 part by mass or greater relative to 100 parts bymass of the abrasive. From the standpoint of increasing the smoothnessof the polished surface (e.g. reducing the haze and defects), thewater-soluble polymer H content to 100 parts by mass of the abrasive issuitably 0.05 part by mass or greater, preferably 0.1 part by mass orgreater, or more preferably 0.5 part by mass or greater (e.g. 1 part bymass or greater). From the standpoint of the polishing rate,washability, etc., the water-soluble polymer H content to 100 parts bymass of the abrasive can be 40 parts by mass or less, or it is usuallysuitably 20 parts by mass or less, preferably 15 parts by mass or less,or more preferably 10 parts by mass or less.

The pH of the produced polishing composition is not particularlylimited. From the standpoint of the great significance of application ofthe art disclosed herein, the pH is suitably 7.5 or higher, preferably8.0 or higher, or more preferably 9.0 or higher (e.g. 9.5 or higher).From the standpoint of easy adjustment of the pH of a polishing liquidcomprising the polishing composition, the polishing composition's pH ispreferably 12.0 or lower, or more preferably 11.0 or lower. It ispreferable to add the basic compound to yield such a pH of the polishingcomposition.

<3-5. Optional Components>

(Optional Polymers)

The polishing composition production method according to the firstaspect disclosed herein can be also preferably applied to production ofa polishing composition comprising, in addition to a water-solublepolymer H, another water-soluble polymer (i.e. a water-soluble polymerfree of an alkaline-hydrolytic functional group, or an “optionalpolymer” hereinafter) as necessary. The type of optional polymer is notparticularly limited. A suitable species can be selected amongwater-soluble polymers that are known in the field of polishingcompositions, but do not belong to the water-soluble polymer H.

The optional polymer may have, in its molecule, at least one species offunctional group selected among cationic groups, anionic groups andnonionic groups. The optional polymer may have, in its molecule, ahydroxyl group, carboxyl group, acyloxy group, sulfo group, amidestructure, quaternary nitrogen structure, heterocyclic structure, vinylstructure, polyoxyalkylene structure, etc. From the standpoint ofreducing aggregates or increasing the washability, etc., a nonionicpolymer can be preferably used as the optional polymer.

Preferable examples of the optional polymer include an oxyalkyleneunit-containing polymer, nitrogen atom-containing polymer,fully-saponified polyvinyl alcohol (typically a polyvinyl alcohol havinga degree of saponification above 98% by mole), and the like.

As the oxyalkylene unit-containing polymer, can be used the same kindsas the oxyalkylene unit-containing polymer described as an example ofthe water-soluble polymer in the polishing composition according to thesecond aspect described above. Examples of the oxyalkyleneunit-containing polymer include a polyethylene oxide (PEO), a blockcopolymer of ethylene oxide (EO) and propylene oxide (PO), a randomcopolymer of EO and PO, and the like. The block copolymer of EO and POcan be a diblock copolymer, triblock copolymer or the like comprising apolyethylene oxide (PEO) block and a polypropylene oxide (PPO) block.Examples of the triblock copolymer include a PEO-PPO-PEO triblockcopolymer and PPO-PEO-PPO triblock copolymer. Usually, a PEO-PPO-PEOtriblock copolymer is more preferable.

In the block or random copolymer of EO and PO, from the standpoint ofthe water solubility and washability, etc., the molar ratio (EO/PO)between EO and PO constituting the copolymer is preferably higher than1, more preferably 2 or higher, or yet more preferably 3 or higher (e.g.5 or higher).

As the nitrogen atom-containing polymer, can be used the same kinds asthe nitrogen atom-containing polymer described as an example of thewater-soluble polymer in the polishing composition according to thesecond aspect described above. As the nitrogen atom-containing polymer,it is possible to use either a polymer containing nitrogen atoms in itsmain chain or a polymer having a nitrogen atom in a side-chainfunctional group (pendant group). Examples of the polymer containingnitrogen atoms in its main chain include a homopolymer and copolymer ofan N-acylalkyleneimine-based monomer. Specific examples of theN-acylalkyleneimine-based monomer include N-acetylethyleneimine,N-propionylethyleneimine, etc. Examples of the polymer having a nitrogenatom in a pendant group include a polymer comprising an N-(meth)acryloylmonomeric unit, a polymer comprising an N-vinyl monomeric unit, etc. Theterm “(meth)acryloyl” herein comprehensively refers to acryloyl andmethacryloyl. For example, a homopolymer and copolymer ofN-(meth)acryloylmorpholine, homopolymer and copolymer ofN-vinylpyrrolidone, and the like can be used.

Other examples of the optional polymer include cellulose derivativessuch as hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethylmethylcellulose, hydroxypropyl methylcellulose, methyl cellulose, ethylcellulose, ethylhydroxyethyl cellulose, carboxymethyl cellulose, etc.;and pullulan.

The molecular weight and molecular weight distribution (Mw/Mn) of theoptional polymer are not particularly limited. For instance, thepreferable Mw and molecular weight distribution in the water-solublepolymer H described above can also be applied to preferable Mw andmolecular weight distribution in the optional polymer.

The optional polymer is used in an amount of suitably 30% by mass orless, preferably 15% by mass or less, or more preferably 10% by mass orless (e.g. 5% by mass or less), of the total amount of water-solublecomponents (including the aforementioned water-soluble polymer H andoptional polymers used as necessary) with Mw of 1×10⁴ or larger. Themethod disclosed herein can be preferably applied to production of apolishing composition essentially free of an optional polymer (e.g. apolishing composition wherein the optional polymer content in the totalamount of the water-soluble components is less than 1% by mass ornon-detectable).

When a cellulose derivative is used as an optional polymer, it is usedin an amount preferably as low as or lower than 10% by mass of the totalamount of water-soluble components with Mw of 1×10⁴ or larger in thepolishing composition, or more preferably 5% by mass or lower (typically1% by mass or lower). This can bring about greater inhibition ofcontamination and aggregation due to the use of a naturally-derivedcellulose derivative. The method disclosed herein can be preferablyapplied to production of, for instance, a polishing compositionessentially free of a cellulose derivative (e.g. with less than 1% bymass or non-detectable cellulose derivative content in the total amountof the water-soluble components).

(Surfactant)

The polishing composition produced by the method disclosed herein cancomprise a surfactant (typically a water-soluble organic compound with amolecular weight below 1×10) as necessary. As the surfactant, the samekinds as the surfactant in the polishing composition according to thefirst aspect described above can be used in a similar manner. Forinstance, as the surfactant, an anionic or nonionic species can bepreferably used. From the standpoint of the low foaming characteristicsand the ease of pH adjustment, a nonionic surfactant is more preferable.The molecular weight of the surfactant is typically smaller than 1×10⁴.From the standpoint of the ease of filtration of the polishingcomposition and the washability of the polished article, etc., it ispreferably 9500 or smaller. The surfactant's molecular weight istypically 200 or larger. From the standpoint of the haze reductioneffect, etc., it is preferably 250 or larger, or more preferably 300 orlarger (e.g. 500 or larger). As the surfactant's molecular weight, canbe used the weight average molecular weight (Mw) (aqueous, based onstandard polyethylene glycol) determined by GPC or the molecular weightdetermined from its chemical formula.

When a surfactant is used, its amount used is not particularly limited.In usual, from the standpoint of the washability, etc., the surfactantis used in an amount of suitably 20 parts by mass or less, preferably 15parts by mass or less, or more preferably 10 parts by mass or less (e.g.6 parts by mass or less) relative to 100 parts by mass of the abrasivein the polishing composition. From the standpoint of obtaining greateruse effect of the surfactant, the amount of surfactant used to 100 partsby mass of the abrasive is suitably 0.001 part by mass or greater,preferably 0.005 part by mass or greater, or more preferably 0.01 partby mass or greater (e.g. 0.1 part by mass or greater). Alternatively,from the standpoint of simplifying the composition, essentially nosurfactant may be used.

(Additives)

As far as the effects of the present invention are not significantlyhindered, the polishing composition produced by the method disclosedherein may further comprise as necessary known additives, such aschelating agents, organic acids, organic acid salts, inorganic acids,inorganic acid salts, preservatives, antifungal agents, and so on,usable in polishing compositions (typically in polishing compositionsused for final polishing of silicon wafers). These additives are asdescribed for the polishing composition according to the first aspectabove. Thus, detailed descriptions are omitted.

In the polishing composition production method according to the firstaspect disclosed herein, the timing of adding these optional componentsis not particularly limited. For example, in the embodiments describedabove, they can be included in any of the agents A, B and C.Alternatively, an optional component may be further added (i.e., addedafterwards) to the polishing composition produced by the methoddisclosed herein.

<3-6. Polishing Liquid>

The polishing composition produced by the method disclosed herein issupplied to a polishing object, typically in a polishing liquid formcomprising the polishing composition, and used for polishing thepolishing object. As the polishing liquid, the polishing composition canbe used straight. Alternatively, the polishing composition may befurther diluted to prepare a polishing liquid. In other words, theconcept of polishing composition in the art disclosed herein encompassesboth a polishing liquid (working slurry) supplied to a polishing objectand used for polishing the polishing object and a concentrate (stocksolution of polishing liquid) which is diluted for use as a polishingliquid. The degree of concentration of the concentrate relative to thepolishing liquid is not particularly limited. For instance, it can beabout 1.2-fold to 200-fold by volume, and is usually suitably about1.5-fold to 100-fold (typically 1.5-fold to 50-fold, e.g. 2-fold to40-fold). Other examples of the polishing liquid comprising thepolishing composition produced by the method disclosed herein include apolishing liquid obtained by adjusting the pH of the polishingcomposition.

The abrasive content in the polishing liquid is not particularlylimited. It is typically 0.01% by mass or greater, preferably 0.05% bymass or greater, or more preferably 0.1% by mass or greater. Withincreasing abrasive content, a higher polishing rate can be achieved.From the standpoint of easy application of the production methoddisclosed herein, the abrasive content in the polishing liquid isusually suitably less than 3% by mass, preferably 2% by mass or less, ormore preferably 1% by mass or less.

The pH of the polishing liquid is not particularly limited. From thestandpoint of the great significance of application of the art disclosedherein, the pH is suitably 7.5 or higher, preferably 8.0 or higher, ormore preferably 9.0 or higher (e.g. 9.5 or higher). From the standpointof the smoothness of the polished surface, the polishing liquid's pH ispreferably 12.0 or lower, or more preferably 11.0 or lower. The basiccompound is preferably included so as to yield such a pH of thepolishing liquid. The pH can be preferably applied, for instance, to apolishing liquid used for polishing silicon wafers (e.g. polishingliquid for final polishing).

<3-7. Applications>

Applications of the polishing composition produced by the methoddisclosed herein are the same as the polishing composition according tothe first aspect. Thus, detailed descriptions are omitted.

<3-8. Polishing>

Polishing of a polishing object can be carried out, for instance, asdescribed below.

In particular, a polishing liquid (typically a slurry polishing liquidwhich may be called polishing slurry) is obtained, comprising apolishing composition produced by a method disclosed herein. Theobtaining the polishing liquid may comprise subjecting the polishingcomposition to concentration adjustment (e.g. dilution), pH adjustment,etc., to prepare the polishing liquid. Alternatively, the polishingcomposition may be used straight as the polishing liquid.

Subsequently, the polishing liquid is supplied to a polishing object andpolishing can be performed by a typical method. For instance, for finalpolishing of a silicon wafer, after a lapping step and a first polishingstep, the silicon wafer is set in a general polishing machine, thepolishing liquid is supplied via a polishing pad in the polishingmachine to the surface (surface to be polished) of the silicon water.Typically, while the polishing liquid is continuously supplied, thepolishing pad is pushed against the surface of the silicon wafer, andthe two are moved (e.g. moved in circular motion) in coordination. Viasuch a polishing step, polishing of the polishing object is completed.

The polishing pad(s) used in the polishing step are not particularlylimited. For instance, any of the non-woven fabric type, suede type,abrasive-bearing type, abrasive-free type, etc., can be used.

A polishing step as described above may be part of the productionprocess of a polished article (e.g. a substrate such as a siliconwafer). Accordingly, this specification provides a method for producinga polished article (preferably a method for producing a silicon wafer)comprising the polishing step.

The polished article after the polishing step is typically cleaned. Thecleaning can be carried out, using a suitable cleaning solution. Thecleaning solution used is not particularly limited. Usable examplesinclude SC-1 cleaning solution (a mixture of ammonium hydroxide (NH₄OH),hydrogen peroxide (H₂O₂) and water (H₂O); cleaning with SC-1 cleaningsolution is referred to as “SC-1 cleaning” hereinafter), SC-2 cleaningsolution (a mixture of HCl, H₂O₂ and H₂O) and the like generally used inthe field of semiconductors. The temperature of the cleaning solutioncan be, for instance, room temperature to about 90° C. From thestandpoint of increasing the cleaning efficiency, a cleaning solution atabout 50° C. to 85° C. can be preferably used.

<<4. Polishing Composition Production Method According to SecondAspect>>

The polishing composition production method according to the secondaspect disclosed herein is a method for producing a polishingcomposition, using an abrasive, a basic compound, a water-solublepolymer H having an alkaline-hydrolytic functional group, and water,with the method comprising

a step of obtaining an agent A comprising at least the basic compound;

a step of obtaining an agent B comprising at least the water-solublepolymer H;

a step of mixing at least the agent A and the agent B to prepare apolishing composition stock solution having a concentration of the basiccompound of higher than 0.02 mol/L; and

a step of diluting the polishing composition stock solution to aconcentration of the basic composition of 0.02 mol/L or lower within 24hours after the agent A and the agent B are mixed.

Described in detail below is the polishing composition production methodaccording to the second aspect.

<4-1. Water-Soluble Polymer H>

The polishing composition production method according to the secondaspect disclosed herein is preferably applied to production of apolishing composition comprising a water-soluble polymer (water-solublepolymer H) having an alkaline-hydrolytic functional group (or a“hydrolytic group” hereinafter). The water-soluble polymer H in thepolishing composition production method according to the second aspectis the same as the water-soluble polymer H in the polishing compositionproduction method according to the first aspect described earlier. Thus,redundant descriptions are omitted.

<4-2. Abrasive, Basic Compound, Water>

The abrasive, the basic compound and water that can be used in thepolishing composition production method according to the second aspectdisclosed herein are the same as the abrasive, the basic compound andwater that can be used in the polishing composition production methodaccording to the first aspect described earlier. Thus, redundantdescriptions are omitted.

<4-3. Production of Polishing Composition>

The polishing composition production method according to the secondaspect disclosed herein can be implemented, using an abrasive, a basiccompound, a water-soluble polymer H and water as described earlier. Inthe production method, an agent A comprising at least the basic compoundand an agent B comprising the water-soluble polymer H are obtained; andat least the agent A and the agent B are mixed to prepare a polishingcomposition stock solution that satisfies one or each of the followingconditions (A) and (B):

(A) having a concentration of the basic compound above 0.02 mol/L.

(B) having a concentration of the abrasive of 1% by mass or higher.

The polishing composition stock solution is diluted within 24 hours fromits preparation. With respect to a polishing composition stock solutionthat satisfies the condition (A), the dilution is preferably carried outso as to yield a concentration of the basic compound of 0.02 mol/L orlower. With respect to a polishing composition stock solution thatsatisfies the condition (B), the dilution is preferably carried out soas to yield a concentration of the abrasive of lower than 1% by mass.

The polishing composition produced by the method disclosed herein showsexcellent temporal stability of polishing performance despite of beingbasic. In the method, the time from the preparation of the polishingcomposition stock solution to the dilution of the stock solution issubject to certain limitations. On the other hand, no particularlimitations are imposed on the time from obtaining the agents A and B tomixing them or the time (storage time) from the preparation of thepolishing composition by diluting the polishing composition stocksolution up to the use of the polishing composition. In other words, byrestricting the time from the preparation of the polishing compositionstock solution to the dilution of the stock solution to a basic compoundconcentration of 0.02 mol/L or lower or to an abrasive concentration oflower than 1% by mass, the flexibility of other processes related to thepolishing composition production can be increased. In addition, sincethe polishing composition is prepared by first preparing the polishingcomposition stock solution having a basic compound concentration above0.02 mol/L or an abrasive concentration of 1% by mass or higher followedby diluting the stock solution, it is highly convenient in theproduction, distribution, storage, etc., of the materials used forpreparation of the stock solution, making it preferable also from thestandpoint of reducing the production costs.

In the art disclosed herein, specifically, the time from the preparationof the polishing composition stock solution to the dilution of the stocksolution is suitably 24 hours or less, preferably 20 hours or less, ormore preferably 16 hours or less. With the time being 12 hours or less(e.g. 8 hours or less), greater effect can be obtained by applying theproduction method disclosed herein. The lower limit of the time is notparticularly limited. For instance, the time from the preparation of thestock solution to the dilution can be 30 seconds or less. Although notparticularly limited to, in a preferable embodiment, from the standpointof taking advantage of the convenience of preparing the polishingcomposition stock solution first and then diluting the stock solution toprepare a polishing composition, the time from the preparation of thestock solution to the dilution can be set to about 1 hour to 10 hours(e.g. 2 hours to 8 hours).

In an embodiment of the preparation of the polishing compositionsatisfying the condition (A), the basic compound concentration of thestock solution is not particularly limited as long as it is higher than0.02 mol/L. From the standpoint of the convenience and reduction ofcosts of production, distribution, storage, etc., of the polishingcomposition stock solution or materials used in its preparation, etc.,the basic compound concentration in the stock solution is preferably0.03 mol/L or higher, or more preferably 0.05 mol/L or higher. The upperlimit of basic compound concentration in the stock solution is notparticularly limited. For instance, it can be 0.4 mol/L or lower. Tolower the rate of hydrolysis of the water-soluble polymer H, in usual,the basic compound concentration is suitably 0.3 mol/L or lower, orpreferably 0.15 mol/L or lower.

The polishing composition stock solution satisfying the condition (A) ispreferably diluted so that the resulting dilution has a basic compoundconcentration of 0.02 mol/L or lower. Preferable basic compoundconcentrations in the dilution may vary also in accordance with thebasic compound concentration of the polishing composition to beproduced. In usual, it is preferably 0.015 mol/L or lower, or morepreferably 0.01 mol/L or lower. In a preferable embodiment, the basiccompound concentration of the dilution can be about the same as thebasic compound concentration of the polishing composition to beproduced. Alternatively, for instance, the dilution may be prepared tohave a slightly higher basic compound concentration (e.g. by about 1 to10% by mass) than the polishing composition to be produced; and afterthe stock solution is diluted within the prescribed time period to abasic compound concentration of 0.02 mol/L or lower, water may befurther added at a certain timing to adjust the basic compoundconcentration.

In an embodiment of the preparation of the polishing composition stocksolution satisfying the condition (B), the abrasive concentration in thestock solution is not particularly limited as long as it is 1% by massor higher. From the standpoint of the convenience and reduction of costsof production, distribution, storage, etc., of the polishing compositionstock solution or materials used in its preparation, etc., the abrasiveconcentration in the stock solution is preferably 2% by mass or higher,or more preferably 3% by mass or higher. The upper limit of abrasiveconcentration in the stock solution is not particularly limited. Forinstance, it can be 50% by mass or lower. From the standpoint of betterpreventing local aggregation of the abrasive, etc., in usual, theabrasive concentration is suitably 40% by mass or lower, preferably 30%by mass or lower, or more preferably 25% by mass or lower (e.g. 20% bymass or lower).

The polishing composition satisfying the condition (B) is preferablydiluted so that the resulting dilution has an abrasive concentration oflower than 1% by mass. Preferable abrasive concentrations in thedilution may vary also in accordance with the abrasive concentration ofthe polishing composition to be produced. In usual, it is preferably0.9% by mass or lower, or more preferably 0.8% by mass or lower (e.g.0.7% by mass or lower). In a preferable embodiment, the abrasiveconcentration of the dilution can be about the same as the abrasiveconcentration of the polishing composition to be produced.Alternatively, for instance, the dilution may be prepared to have aslightly higher abrasive concentration (e.g. by about 1 to 10% by mass)than the polishing composition to be produced; and after the stocksolution is diluted within the prescribed time period to an abrasiveconcentration of lower than 1% by mass, water may be further added at acertain timing to adjust the abrasive concentration.

The polishing composition stock solution can be diluted by a dilutionfactor of, for instance, suitably greater than 3 up to about 200,usually preferably about 5 to 100, or more preferably about 10 to 70(e.g. about 15 to 50).

The basic compound content in the polishing composition stock solutionis preferably 0.01% by mass or greater, or more preferably 0.03% by massor greater. With increasing basic compound content, the dispersionstability of the abrasive tends to increase. The basic compound contentin the stock solution is preferably 10% by mass or less, more preferably5% by mass or less, or yet more preferably 3% by mass or less. Withdecreasing basic compound content, it becomes easier to adjust the basiccompound content in the polishing composition.

The pH of the polishing composition stock solution is preferably 9 orhigher, or more preferably 9.5 or higher. With increasing pH, thedispersion stability of the abrasive tends to increase. In general, at ahigher pH, the rate of hydrolysis of the water-soluble polymer Hincreases. Thus, it may be more meaningful to apply the productionmethod disclosed herein. The stock solution's pH is preferably 12 orlower, more preferably 11.5 or lower, or yet more preferably 10.5 orlower. When the stock solution's pH is set lower, it becomes easier toadjust the basic compound content in the polishing composition. Forinstance, when the abrasive is silica grains, it is also advantageousthat the pH is not excessively high, from the standpoint of reducingdissolution of the silica.

The water-soluble polymer H content (concentration) in the polishingcomposition stock solution is preferably 0.02% by mass or greater, morepreferably 0.05% by mass or greater, or yet more preferably 0.1% by massor greater. With increasing water-soluble polymer H content, it becomeseasier to adjust the water-soluble polymer H content in the polishingcomposition. The water-soluble polymer H content in the stock solutionis preferably 20% by mass or less. For example, it can be 15% by mass orless. With decreasing water-soluble polymer H content, local aggregationof the abrasive tends to be inhibited to a greater extent.

Typical embodiments of the polishing composition production methodaccording to the second aspect disclosed herein is described withrespect to an example of producing a polishing composition, using silicagrains as the abrasive, ammonia as the basic compound and apartially-saponified polyvinyl alcohol (degree of saponification 73% bymole) as the water-soluble polymer H, but the embodiments and productsof the present invention are not limited by these.

First Embodiment

In this embodiment, a polishing composition is produced, using apolishing composition preparation kit in which the following agents Aand B are separately stored:

Agent A: an abrasive dispersion comprising an abrasive, a basic compoundand water (a basic abrasive dispersion with 3 to 25% by mass abrasivecontent at a basic compound concentration of 0.02 mol/L to 1 mol/L)

Agent B: an aqueous solution of a water-soluble polymer H (an aqueouspolymer solution with 0.02 to 50% by mass polymer content at about pH 6)

Specifically, for instance, the agent B is added to the agent A andmixed to prepare a polishing composition stock solution that satisfiesat least either the basic compound concentration being higher than 0.02mol/L or the abrasive concentration being 1% by mass or higher. Withinan aforementioned preferable time period from the preparation of thestock solution, by adding ultrapure water to the stock solution to aconcentration that satisfies at least either the basic compoundconcentration being 0.02 mol/L or lower or the abrasive concentrationbeing lower than 1% by mass, a polishing composition can be producedwith excellent storage stability.

Because the agent A used in this embodiment is in a state where theabrasive and the basic compound are co-present, the abrasive hasincreased electrostatic repulsion due to the basic compound and therebyexhibits high dispersion stability. Thus, when mixed with the agent B,local aggregation of the abrasive can be highly prevented.

The agent B used in this embodiment is prepared as an aqueous solutionin which the water-soluble polymer H has been dissolved in water inadvance. Accordingly, when mixed with the agent A, local aggregation ofthe abrasive can be highly prevented. This is preferable from thestandpoint of increasing the ease of filtration of a polishingcomposition produced according to the present embodiment or reducingdefects in the polished surface.

The agents A and B used in this embodiment are in concentrated forms(wherein at least either the abrasive concentration or the basiccompound concentration is higher) when compared with the polishingcomposition to be produced. Thus, it is advantageous from the standpointof the convenience and reduction of costs of production, distribution,storage, etc.

The abrasive content in the agent A can be, for instance, 50% by mass orless. From the standpoint of preventing local aggregation of theabrasive to a greater extent, in usual, the abrasive concentration issuitably 40% by mass or lower, preferably 30% by mass or lower, or yetmore preferably 25% by mass or lower (e.g. 20% by mass or lower). Fromthe standpoint of the convenience and reduction of costs of production,distribution, storage, etc., the abrasive content in the agent A is, forinstance, suitably greater than 2% by mass, or preferably greater than3% by mass.

The basic compound content in the agent A is preferably 0.01% by mass orgreater, more preferably 0.05% by mass or greater, or yet morepreferably 0.1% by mass or greater. With increasing basic compoundcontent, local aggregation tends to be inhibited to a greater extentwhen mixed with the agent B. The basic compound content in the agent Ais preferably 10% by mass or less, more preferably 5% by mass or less,or yet more preferably 3% by mass or less. With decreasing basiccompound content, it becomes easier to adjust the basic compound contentin the polishing composition.

The agent A has a pH of preferably 9 or higher, or more preferably 9.5or higher. With increasing pH, local aggregation tends to be inhibitedto a greater extent when mixed with the agent B. In general, at a higherpH, the rate of hydrolysis of the water-soluble polymer H increases.Thus, it may be more meaningful to apply the production method disclosedherein. The agent A has a pH of preferably 12 or lower, more preferably11.5 or lower, or yet more preferably 10.5 or lower. When the agent A'spH is set low, it becomes easier to adjust the basic compound content inthe polishing composition. For instance, when the abrasive is siliconparticles, the pH being not exceedingly high is advantageous also fromthe standpoint of inhibiting dissolution of the silica. The agent A's pHcan be adjusted by the amount (concentration) of the basic compoundadded and so on.

The water-soluble polymer H content (concentration) in the agent B ispreferably 0.02% by mass or greater, more preferably 0.05% by mass orgreater, or yet more preferably 0.1% by mass or greater. With increasingwater-soluble polymer H content, it becomes easier to adjust thewater-soluble polymer H content in the polishing composition. Thewater-soluble polymer H content in the agent B is preferably 50% by massor less, and can be, for instance, 20% by mass or less. With decreasingwater-soluble polymer H content, local aggregation of the abrasive tendsto be inhibited to a greater extent when the agent B is added to thediluted agent A.

From the standpoint of inhibiting hydrolysis of the water-solublepolymer H, the agent B is preferably formulated to a near-neutral pH ingeneral. The agent B's pH is usually preferably 4 or higher, but lowerthan 9, or more preferably 5.5 to 7.5. The art disclosed herein can beimplemented, for instance, in an embodiment wherein the agent B's pH isaround 6 (e.g. 6±0.3). In a preferable embodiment, the agent B can beprepared in a composition essentially free of a basic compound (e.g. acomposition consisting of a water-soluble polymer H and water).

The agents A and B are preferably mixed in an embodiment where the agentB is added to the agent A as described earlier. According to such amixing method, local aggregation of the abrasive can be prevented to agreater extent as compared with, for instance, a mixing method where theagent A is added to the agent B. When the abrasive is silica grains(e.g. colloidal silica grains), as described above, it is particularlymeaningful to employ the mixing method where the agent B is added to theagent A.

The agent B is added to the agent A at a rate (supply rate) ofpreferably, to a liter (1 L) of agent A, 500 mL of agent B per minute orlower, more preferably 100 mL/min or lower, or yet more preferably 50mL/min or lower. By decreasing the supply rate, local aggregation of theabrasive can be inhibited to a greater extent.

For preparing the agents A and B, adding the agent A to the agent B andmixing, or diluting the polishing composition stock solution, etc., theapparatus used is not particularly limited. For instance, a known mixercan be used, such as a propeller mixer, ultrasonic disperser, homomixerand the like. In a preferable embodiment, the agent B can be filteredbefore mixed with the agent A. The filtration method is not particularlylimited. For instance, can be suitably employed natural filtrationcarried out at normal pressure or a known filtration method such assuction filtration, pressure filtration, centrifugal filtration, etc.

Second Embodiment

In this embodiment, a polishing composition is produced, using apolishing composition preparation kit in which the following agents A, Band C are stored separately:

Agent A: an aqueous solution of a basic composition (an aqueous solutionat a basic composition concentration of 0.02 mol/L or higher)

Agent B: an aqueous solution of a water-soluble polymer H (an aqueouspolymer solution at a polymer concentration of 0.02 to 50% by mass atabout pH 6)

Agent C: a dispersion comprising an abrasive and water (an abrasivedispersion with 3 to 25% by mass abrasive content)

Specifically, for instance, the agents A and C are mixed to prepare abasic abrasive dispersion comprising the abrasive and basic compound.The agent B is added to the dispersion and mixed to prepare a polishingcomposition stock solution that satisfies at least either the basiccompound concentration being higher than 0.02 mol/L or the abrasiveconcentration being 1% by mass or higher. A polishing composition withexcellent storage stability can be produced by adding ultrapure water tothe stock solution within an aforementioned preferable time period afterthe preparation of the stock solution to dilute it to a concentrationthat satisfies at least either the basic compound concentration being0.02 mol/L or lower or the abrasive concentration being lower than 1% bymass.

<4-4. Polishing Composition>

In typical, the polishing composition production method disclosed hereincan be preferably applied to production of a polishing composition(typically a slurry composition) having a non-volatile content (NV) of2% by mass or less. More preferably, it is applied to production of apolishing composition having an NV of 0.05% by mass to 1% by mass (e.g.0.05 to 0.8% by mass). The non-volatile content (NV) refers to theproportion of the mass of residue remaining after a polishingcomposition is allowed to dry at 105° C. for 24 hours in the polishingcomposition. In typical, the method disclosed herein can be preferablyapplied to production of a polishing composition having an abrasivecontent of less than 1% by mass. A preferable target product is apolishing composition having an abrasive content of 0.05 to 0.9% by mass(more preferably 0.05 to 0.8% by mass).

The water-soluble polymer H content in the polishing compositionproduced by the method disclosed herein is not particularly limited. Forinstance, it can be 1×10⁻⁴% by mass or greater. From the standpoint ofhaze reduction, etc., the polymer H content is preferably 5×10⁻⁴% bymass or greater, or more preferably 1×10⁻³% by mass or greater, forexample, 2×10⁻³% by mass or greater. From the standpoint of thepolishing rate, etc., the polymer H content is preferably 0.5% by massor less, or more preferably 0.2% by mass or less (e.g. 0.1% by mass orless).

The water-soluble polymer H content can be, but not particularly limitedto, for instance, 0.01 part by mass or greater relative to 100 parts bymass of the abrasive. From the standpoint of increasing the smoothnessof the polished surface (e.g. reducing the haze and defects), thewater-soluble polymer H content to 100 parts by mass of the abrasive issuitably 0.05 part by mass or greater, preferably 0.1 part by mass orgreater, or more preferably 0.5 part by mass or greater (e.g. 1 part bymass or greater). From the standpoint of the polishing rate,washability, etc., the water-soluble polymer H content to 100 parts bymass of the abrasive can be 40 parts by mass or less, or it is usuallysuitably 20 parts by mass or less, preferably 15 parts by mass or less,or more preferably 10 parts by mass or less.

The pH of the produced polishing composition is not particularlylimited. From the standpoint of the great significance of application ofthe art disclosed herein, the pH is suitably 7.5 or higher, preferably8.0 or higher, or more preferably 9.0 or higher (e.g. 9.5 or higher).From the standpoint of easy adjustment of the pH of a polishing liquidcomprising the polishing composition, the polishing composition's pH ispreferably 12.0 or lower, or more preferably 11.0 or lower. It ispreferable to add the basic compound to yield such a pH of the polishingcomposition.

<4-5. Optional Components>

(Optional Polymers)

The art disclosed herein can be also preferably applied to production ofa polishing composition comprising, in addition to a water-solublepolymer H, another water-soluble polymer having a Mw of 1×10⁴ or larger(i.e. a water-soluble polymer free of an alkaline-hydrolytic functionalgroup, or an “optional polymer” hereinafter) as necessary. The type ofoptional polymer is not particularly limited. A suitable species can beselected among water-soluble polymers that are known in the field ofpolishing compositions, but do not belong to the water-soluble polymerH.

The type, molecular weight and molecular weight distribution (Mw/Mn),usage, etc., of such an optional polymer are the same as in thepolishing composition production method according to the first aspectdescribed earlier. Thus, detailed descriptions are omitted.

(Surfactant)

The polishing composition produced by the method disclosed herein cancomprise a surfactant (typically a water-soluble organic compound with amolecular weight below 1×10) as necessary. The type, specific examples,molecular weight, usage, etc., of surfactant are the same as thesurfactant in the polishing composition according to the first aspectdescribed above. Thus, detailed descriptions are omitted.

(Additives)

As far as the effects of the present invention are not significantlyhindered, the polishing composition produced by the method disclosedherein may further comprise as necessary known additives, such aschelating agents, organic acids, organic acid salts, inorganic acids,inorganic acid salts, preservatives, antifungal agents, and so on,usable in polishing compositions (typically in polishing compositionsused for final polishing of silicon wafers). These additives are asdescribed for the polishing composition according to the first aspectabove. Thus, detailed descriptions are omitted.

In the polishing composition production method disclosed herein, thetiming of adding these optional components is not particularly limited.For example, in the embodiments described above, they can be included inany of the agents A, B and C. Alternatively, an optional component maybe further added (i.e., added afterwards) to the polishing compositionproduced by the method disclosed herein.

<4-6. Polishing Liquid>

The polishing composition produced by the method disclosed herein issupplied to a polishing object, typically in a polishing liquid formcomprising the polishing composition, and used for polishing thepolishing object. As the polishing liquid, the polishing composition canbe used straight. Alternatively, the polishing composition may befurther diluted to prepare a polishing liquid. In other words, theconcept of polishing composition in the art disclosed herein encompassesboth a polishing liquid (working slurry) supplied to a polishing objectand used for polishing the polishing object and a concentrate which isdiluted for use as a polishing liquid. The degree of concentration ofthe concentrate relative to the polishing liquid is not particularlylimited. For instance, it can be about 1.05-fold to 200-fold by volume,and is usually preferably about 1.2-fold to 100-fold, or more preferablyabout 1.5-fold to 70-fold. Other examples of the polishing liquidcomprising the polishing composition produced by the method disclosedherein include a polishing liquid obtained by adjusting the pH of thepolishing composition.

The abrasive content in the polishing liquid is not particularlylimited. It is typically 0.01% by mass or greater, preferably 0.05% bymass or greater, or more preferably 0.1% by mass or greater. Withincreasing abrasive content, a higher polishing rate can be achieved.From the standpoint of easy application of the production methoddisclosed herein, the abrasive content in the polishing liquid isusually suitably less than 1% by mass, preferably 0.8% by mass or less,or more preferably 0.6% by mass or less.

The pH of the polishing liquid is not particularly limited. From thestandpoint of the great significance of application of the art disclosedherein, the pH is suitably 7.5 or higher, preferably 8.0 or higher, ormore preferably 9.0 or higher (e.g. 9.5 or higher). From the standpointof the smoothness of the polished surface, the polishing liquid's pH ispreferably 12.0 or lower, or more preferably 11.0 or lower. The basiccompound is preferably included so as to yield such a pH of thepolishing liquid. The pH can be preferably applied, for instance, to apolishing liquid used for polishing silicon wafers (e.g. polishingliquid for final polishing).

<4-7. Applications, Polishing and Cleaning>

Applications of the polishing composition produced by the polishingcomposition production method according to the second aspect disclosedherein, polishing with the polishing composition and cleaning thepolished article in the polishing step are the same as the polishingcomposition produced by the polishing composition production methodaccording to the first aspect described above. Thus, detaileddescriptions are omitted.

As understood from the descriptions provided above and the workingexamples below, matters disclosed by this specification include thefollowing:

(1) A method for producing a polishing composition, using water and awater-soluble polymer P that comprises, in its molecular structure, arepeat unit f having a hydrolytic functional group; the methodcharacterized in that in the polishing composition produced, the ratiom_(d)/m_(T) (herein, m_(f) represents the number of moles of the repeatunit f, and m_(T) represents the number of moles of all repeat unitscombined in the water-soluble polymer P) is maintained at or above 5%.(2) A method for producing a polished article, with the methodcomprising a step of supplying the polishing composition produced by themethod (1) above and polishing the polishing object, with the methodcharacterized in that the water-soluble polymer P in the polishingcomposition supplied to the polishing object maintains the ratiom_(f)/m_(T) of 5% or greater.

The repeat unit f may be a functional group that is hydrolytic underacidic or basic conditions. A typical example of such a functional groupis ester group. Typical examples of the ester group-containing repeatunit f include homopolymers and copolymers of vinyl carboxylates and(meth)acrylic acid esters as well as modification products (e.g.saponification products) of these, and the like. The polishingcomposition may comprise, besides the water-soluble polymer P and water,any one, two or more among abrasives, basic compounds and acidiccompounds as optional component(s).

The production method (1) can be implemented, for instance, by applyinga production method disclosed herein (e.g. the first to thirdembodiments of the production method according to the first aspect, thefirst and second embodiments of the production method according to thesecond aspect, and production methods according to modification examplesof these) although not limited to these.

As understood from the descriptions provided above and the workingexamples below, matters disclosed by this specification further includethe following:

(3) A method for producing a polishing composition, using water and awater-soluble polymer Q that comprises a repeat unit h having a hydroxylgroup, the method characterized in that in the polishing compositionproduced, the water-soluble polymer Q has a hydroxyl group content of 4mmol/g or greater, but 21 mmol/g or less.(4) A method for producing a polished article, the method comprising astep of supplying the polishing composition produced by the method (3)above and polishing the polishing object and the method characterized inthat in the water-soluble polymer Q in the polishing compositionsupplied to the polishing object, the water-soluble polymer Q has ahydroxyl group content in a range of 4 mmol/g or greater, but 21 mmol/gor less.

Herein, the hydroxyl group content refers to the number of moles ofhydroxyl groups contained in one gram of the polymer. The hydroxyl groupcontent can be generally obtained by subjecting a sample solutioncomprising the polymer of interest to neutralization titration asspecified in JIS K0070 to determine the hydroxyl value (mgKOH/g) anddividing the hydroxyl value by 56.1.

When the polymer of interest is, for instance, a polymer formed of vinylcarboxylate units and vinyl alcohol units such as a partially-saponifiedpolyvinyl alcohol, the hydroxyl group content can also be determined asfollows. Namely, potassium hydroxide (KOH) is added to the samplesolution containing the polymer of interest and the resulting solutionis heated to allow complete saponification; the amount of KOH consumedduring this is determined by titration; from the results, the number ofmoles of vinyl carboxylate units and the number of moles of vinylalcohol units are determined; and from their numbers of moles, thehydroxyl group content can be determined.

In measuring the hydroxyl group content, when a polymer contained in apolishing composition is measured, the polishing composition can be usedas the sample solution. When the polishing composition comprises anabrasive, the abrasive is precipitated by centrifugation and theresulting supernatant can be used as the sample solution.

Matters disclosed by this description include the following:

(1) A polishing composition comprising a water-soluble polymer thatsatisfies the following conditions:

having a molecular structure comprising a plurality of repeat unitspecies with different types of unit species; and

the plurality of repeat unit species comprising a repeat unit A and arepeat unit B which is different from the repeat unit A.

(2) The polishing composition according to (1) above, wherein thewater-soluble polymer is a nonionic polymer.

(3) A polishing composition comprising an abrasive, a water-solublepolymer and water, the polishing composition exhibiting an etching rateof 2.0 nm/min or lower based on the following etching rate measurement:

(1A) an etching rate measuring reagent LE is obtained, comprising 0.18%by mass of the water-soluble polymer and 1.3% by mass of ammonia withthe rest being water;

(2A) a silicon substrate (in a 6 cm long by 3 cm wide by 775 μm thickrectangle) is obtained, from which surface natural oxide film isremoved, and its mass W0 is measured;

(3A) the silicon substrate is immersed in the reagent LE at roomtemperature for 12 hours;

(4A) the silicon substrate is removed from the reagent LE and cleaned atroom temperature for 10 seconds with a cleaning solution formed of NH₃(29%)/H₂O₂ (31%)/ultrapure water=1/1/8 (volume ratio);

(5A) the cleaned silicon substrate is measured for its mass W1; and

(6A) from the difference between the W0 and W1 as well as the specificgravity of the silicon substrate, the etching rate (nm/min) isdetermined;

and also has an abrasive adsorption of 20% or lower based on thefollowing abrasive adsorption measurement:

(1B) the polishing composition is centrifuged to precipitate theabrasive and the resulting supernatant is subjected to measurement oftotal organic carbon to determine the total amount of organic carbon,C1, in the supernatant;

(2B) a test solution L0 is obtained having the same composition as thatof the polishing composition but without the abrasive, and the testsolution L0 is subjected to measurement of total organic carbon todetermine the total amount of organic carbon, C0, in the test solutionL0; and

(3B) from the C0 and C1, the abrasive adsorption is determined by thefollowing equation:Abrasive adsorption (%)=[(C0−C1)/C0]×100.(4) The polishing composition according to (3) above, wherein thewater-soluble polymer is a nonionic polymer.(5) The polishing composition according to (3) or (4) above, wherein thewater-soluble polymer has a molecular structure comprising both of avinyl alcohol unit and a vinyl acetate unit as the repeat units.(6) A method for producing a polishing composition, using an abrasive, abasic compound and a water-soluble polymer H having a functional groupthat is hydrolytic under basic conditions, and water; the methodcomprising:

a step of obtaining an agent A that comprises at least the basiccompound;

a step of obtaining an agent B that comprises at least the water-solublepolymer H; and

a step of mixing a first composition comprising at least the agent A anda second composition comprising at least the agent B to prepare amixture that comprises the abrasive, the basic compound, thewater-soluble polymer H and water at a concentration of the basiccompound of 0.1 mol/L or lower.

(7) The method for producing the polishing composition according to (6)above, wherein

the agent A is an abrasive dispersion C comprising the abrasive, thebasic compound and water, and

the abrasive dispersion C is diluted to prepare the first composition;and then, the first composition is mixed with the second composition toprepare the mixture.

(8) A method for producing a polishing composition, using an abrasive, abasic compound, a water-soluble polymer H having a functional group thatis hydrolytic under basic conditions, and water; the method comprising

a step of obtaining an agent A comprising at least the basic compound;

a step of obtaining an agent B comprising at least the water-solublepolymer H; and

a step of mixing a first composition comprising at least the agent A anda second composition comprising at least the agent B to prepare amixture that comprises the abrasive, the basic compound, thewater-soluble polymer H and water at a concentration of the abrasive oflower than 3% by mass.

(9) The method for producing the polishing composition according to (8)above, wherein

the agent A is an abrasive dispersion C comprising the abrasive, thebasic compound and water, and

the abrasive dispersion C is diluted to prepare the first composition;and then, the first composition is mixed with the second composition toprepare the mixture.

(10) A polishing composition preparation kit used in the methodaccording to any one of (6) to (9) above, comprising the agent A and theagent B that are stored separately.

(11) A method for producing a polishing composition, using an abrasive,a basic compound and a water-soluble polymer H having a functional groupthat is hydrolytic under basic conditions, and water; the methodcomprising:

a step of obtaining an agent A that comprises at least the basiccompound;

a step of obtaining an agent B that comprises at least the water-solublepolymer H;

a step of mixing at least the agent A and the agent B to prepare apolishing composition stock solution having a concentration of the basiccompound of higher than 0.02 mol/L; and

a step of diluting the polishing composition stock solution to aconcentration of the basic composition of 0.02 mol/L or lower within 24hours after the agent A and the agent B are mixed.

(12) A method for producing a polishing composition, using an abrasive,a basic compound, a water-soluble polymer H having a functional groupthat is hydrolytic under basic conditions, and water; the methodcomprising:

a step of obtaining an agent A that comprises at least the basiccompound;

a step of obtaining an agent B that comprises at least the water-solublepolymer H;

a step of mixing at least the agent A and the agent B to prepare apolishing composition stock solution having an abrasive content of 1% bymass or greater; and

a step of diluting the polishing composition stock solution to anabrasive content of less than 1% by mass within 24 hours after the agentA and the agent B are mixed.

(13) The method for producing the polishing composition according to(11) or (12) above, wherein the stock solution is diluted by a factor of10 or greater by volume in the step of diluting the polishingcomposition stock solution.

(14) A polishing composition preparation kit used in the methodaccording to any one of (11) to (13) above, comprising the agent A andthe agent B that are stored separately.

EXAMPLES

Several working examples relating to the present invention are describedbelow although the present invention is not to be limited to suchworking examples. In the description below, “parts” and “%” are based onmass unless otherwise specified.

Experiment 1

<Preparation of Polishing Compositions>

Example A1

An abrasive, a water-soluble polymer HA and aqueous ammonia (29%concentration) and ultrapure water were mixed to prepare a polishingcomposition concentrate. Within one hour from the mixing, theconcentrate was diluted by a factor of 20 (by volume) with ultrapurewater to prepare a polishing composition containing 0.5% abrasive,0.010% ammonia (NH₃) and 0.018% water-soluble polymer HA with the restbeing water. The polishing composition had a pH of 10.2.

As the abrasive, was used a colloidal silica of 35 nm average primaryparticle diameter and 66 nm average secondary particle diameter. Theaverage primary particle diameter was measured with a surface areaanalyzer under trade name “FLOW SORB II 12300” available fromMicromeritics. The average secondary particle diameter was the volumeaverage secondary particle diameter measured with a model “UPA-UT151”available from Nikkiso Co., Ltd. (the same applies to the examplesbelow).

As the water-soluble polymer HA, was used a polyvinyl alcohol having adegree of saponification of 73% by mole and a weight average molecularweight (Mw) of 2.8×10⁴. The molar ratio of vinyl alcohol units in thewater-soluble polymer HA, namely the ratio of number of moles of vinylalcohol units to number of moles of all repeat units, is 73%. The molarratio of vinyl acetate units in the water-soluble polymer HA is 27%.

Example A2

In this example, as the abrasive, was used a colloidal silica of 25 nmaverage primary particle diameter and 46 nm average secondary particlediameter. With ultrapure water, were mixed the abrasive and ammoniawater (29% concentration) to prepare a polishing compositionconcentrate. Within one hour after the mixing, the concentrate wasdiluted by a factor of 20 (by volume) with ultrapure water to prepare apolishing composition having 0.2% abrasive, 0.005% ammonia and 0.010%water-soluble polymer HA with the rest being water. The polishing liquidhad a pH of 10.1.

The concentrations of water-soluble polymer HA and ammonia in thepolishing composition of this example were adjusted so that thewater-soluble polymer and ammonia contents relative to the surface areaof the abrasive in the unit volume of the polishing liquid wereapproximately equal to those in the polishing liquid of Example A1.

Example A3

In this example, in place of water-soluble polymer HA in Example A1, wasused a polyvinyl alcohol (water-soluble polymer HB) with a degree ofsaponification of 78% by mole and a Mw of 2.7×10⁴. Otherwise, in thesame manner as Example A1, a polishing composition according to thisexample was prepared.

The molar ratio of vinyl alcohol units in the water-soluble polymer HBis 78%. The molar ratio of vinyl acetate units in the water-solublepolymer HB is 22%.

Example A4

In this example, in place of water-soluble polymer HA in Example A1, wasused a polyvinyl alcohol with a Mw of 2.8×10⁴ (containing 80% by molevinyl alcohol units and 20% by mole vinyl hexanoate units;“water-soluble polymer HJ” hereinafter). Otherwise, in the same manneras Example A1, a polishing composition according to this example wasprepared.

Example A5

In this example, in place of water-soluble polymer HA in Example A1, wasused a polyvinyl alcohol with a Mw of 0.3×10⁴ (containing 80% by molevinyl alcohol units and 20% by mole vinyl hexanoate units;“water-soluble polymer HK” hereinafter). The water-soluble polymer HKconcentration of the polishing composition was 0.003%. Otherwise, in thesame manner as Example A1, a polishing composition according to thisexample was prepared.

Example A6

In this example, in place of water-soluble polymer HA in Example A2, wasused a water-soluble polymer HC with a Mw of 2.1×10⁴.

The molar ratio of vinyl alcohol units in the water-soluble polymer HCis 90%. The molar ratio of vinyl acetate units in the water-solublepolymer HC is 10%.

Example A7

In this example, in place of water-soluble polymer HA in Example A2, wasused a water-soluble polymer HD with a Mw of 2.1×10⁴.

The molar ratio of vinyl alcohol units in the water-soluble polymer HDis 90%. The molar ratio of butyl vinyl ether units in the water-solublepolymer HD is 10%.

Comparative Example A1

In this example, in place of water-soluble polymer HA in Example A1, wasused a fully-saponified polyvinyl alcohol (polyvinyl alcohol with adegree of saponification of 98% by mole and a Mw of 2.2×10⁴;water-soluble polymer HE, hereinafter). Otherwise, in the same manner asExample A1, a polishing composition according to this example wasprepared.

The molar ratio of vinyl alcohol units in the water-soluble polymer HEis 98%. The molar ratio of vinyl acetate units in the water-solublepolymer HE is 2%.

Comparative Example A2

In this example, in place of water-soluble polymer HA in Example A1, wasused an acrylamide/acrylic acid random copolymer (water-soluble polymerHF). Otherwise, in the same manner as Example A1, a polishingcomposition according to this example was prepared.

The water-soluble polymer HF is a copolymer with a Mw of 20×10⁴,comprising an acrylic acid-derived repeat unit and an acrylamide-derivedrepeat unit at a molar ratio of 40:60.

Comparative Example A3

In this example, in place of water-soluble polymer HA in Example A1, wasused an ethylene oxide/propylene oxide random copolymer (water-solublepolymer HG). Otherwise, in the same manner as Example A1, a polishingcomposition according to this example was prepared.

The water-soluble polymer HG is a copolymer with a Mw of 10×10⁴,comprising an ethylene oxide-derived repeat unit and a propyleneoxide-derived repeat unit at a molar ratio of 92:8.

Comparative Example A4

In this example, in place of water-soluble polymer HA in Example A1, wasused a poly(N-vinylpyrrolidone) with a Mw of 6×10⁴ (water-solublepolymer HH). Otherwise, in the same manner as Example A1, a polishingcomposition according to this example was prepared.

The water-soluble polymer HH is a homopolymer of N-vinylpyrrolidone.

Comparative Example A5

In this example, in place of water-soluble polymer HA in Example A1, wasused a hydroxyethyl cellulose with a Mw of 25×10⁴ (water-soluble polymerH1). Otherwise, in the same manner as Example A1, a polishingcomposition according to this example was prepared.

<Silicon Wafer Polishing>

Using the polishing compositions according to the respective examples asthey were as polishing liquids, silicon wafer surfaces were polishedunder the conditions shown below. The silicon wafers used had 300 mmdiameter, p-type conductivity, crystal orientation of <100> and aresistivity of 0.1 Ω·cm or greater, but less than 100 Ω·cm, and werepreliminarily polished with a polishing slurry (trade name “GLANZOX2100” available from Fujimi, Inc.) to a surface roughness of 0.1 nm to10 nm for the use. The time from the preparation of the polishingcomposition to the start of polishing was about one hour.

[Polishing Conditions]

Polishing machine: Sheet-type polisher with model number “PNX-332B”available from Okamoto Machine Tool Works, Ltd.

Polishing tables: Using two rear tables among three tables of thepolishing machine, the first and second stages of final polishing afterthe preliminary polishing were carried out.

(The conditions below were common between the two tables)

Polishing pressure: 15 kPa

Plate rotational speed: 30 rpm

Head rotational speed: 30 rpm

Polishing time: 2 min

Temperature of polishing liquid: 20° C.

Flow rate of polishing liquid: 2.0 L/min (drain)

<Cleaning>

Polished silicon wafers were cleaned (SC-1 cleaned) with a cleaningsolution at NH₄OH (29%)/H₂O₂(31%)/deionized water (DIW)=1/3/30 (volumeratio). More specifically, two cleaning baths each equipped with anultrasonic wave oscillator of 950 kHz frequency were obtained; thecleaning solution was placed in each of the first and second cleaningbaths and maintained at 60° C.; and each polished silicon wafer wasimmersed in the first cleaning bath for 6 minutes and then, via aultrasonic rinsing bath with ultrapure water, in the second cleaningbath for 6 minutes, with the respective ultrasonic wave oscillatorsturned on.

<Assessment of the number of micro particles (LPD)>

Using a wafer inspection system under trade name “SURFSCAN SP2”available from KLA-Tencor Corporation, the number of 37 nm or largerparticles (number of LPD) present on each cleaned silicon wafer of 300mm diameter was counted.

<Haze Measurement>

The surface of each cleaned silicon wafer was measured for haze (ppm) inDWO mode, using a wafer inspection system under trade name “SURFSCANSP2” available from KLA-Tencor Corporation.

The results of the LPD count and haze measurement are converted torelative values and shown in Table 3, with 100% being the number of LPDand haze value of Comparative Example A5 using solely the hydroxyethylcellulose (HEC) as the water-soluble polymer. Table 3 also shows thecompositions of the water-soluble polymers used in the respectiveexamples. In the column for the LPD count, “n/m” (not measured)indicates that the defect analysis with the wafer inspection systemresulted in data overload, that is, the number of LPD exceeded the uppermeasurement limit.

TABLE 3 Water-soluble polymer Hydroxyl First repeat unit Second repeatunit group Properties Molar ratio Molar ratio content Mw Haze LPDSpecies (%) Species (%) (mmol/g) (×10⁴) (%) (%) Ex. A1 Vinyl alcoholgroup 73 Vinyl acetate group 27 13.2 2.8 80 80 Ex. A2 Vinyl alcoholgroup 73 Vinyl acetate group 27 13.2 2.8 70 80 Ex. A3 Vinyl alcoholgroup 78 Vinyl acetate group 22 14.6 2.7 85 85 Ex. A4 Vinyl alcoholgroup 80 Vinyl hexanoate group 20 12.6 2.8 90 80 Ex. A5 Vinyl alcoholgroup 80 Vinyl hexanoate group 20 12.6 0.3 80 80 Ex. A6 Vinyl alcoholgroup 90 Vinyl acetate group 10 18.6 2.1 75 80 Ex. A7 Vinyl alcoholgroup 90 Butyl vinyl ether group 10 18.1 2.1 75 80 Comp. Ex. A1 Vinylalcohol group 98 Vinyl acetate group 2 21.9 2.2 225 200  Comp. Ex. A2Acrylic acid group 40 Acrylamide group 60 0.0 20 500 n/m Comp. Ex. A3Ethylene oxide group 92 Propylene oxide group 8 0.0 10 150 300  Comp.Ex. A4 Poly(N-vinylpyrrolidone) 0.0 6 400 n/m Comp. Ex. A5 Hydroxyethylcellulose 11.5 25 100 100 

As shown in Table 3, the polishing liquids of Examples A1 to A7 showedmarked improvement in both the haze value and the LPD count as comparedwith Comparative Example A5 using HEC as the water-soluble polymer

On the contrary, Comparative Example A1 fell short of Examples A1 to A7in terms of both the haze value and the LPD count. Comparative ExamplesA2, A3 and A4 also fell short of Examples A1 to A7 in terms of both thehaze value and the LPD count.

Experiment 2

<Preparation of Polishing Compositions>

Example B1

To a basic abrasive dispersion with approximately 0.46% NV formed of anabrasive, ammonia and ultrapure water, was added and mixed an aqueouspolymer solution containing 1.5% by mass of water-soluble polymer P1 toprepare a polishing composition having 0.46% abrasive, 0.010% ammonia(NH₃) and 0.018% water-soluble polymer HA with the rest being water. Thepolishing composition had a pH of 10.2.

As the abrasive, was used a colloidal silica of 35 nm average primaryparticle diameter and 66 nm average secondary particle diameter. Theaverage primary particle diameter was measured with a surface areaanalyzer under trade name “FLOW SORB II 12300” available fromMicromeritics. The average secondary particle diameter was the volumeaverage secondary particle diameter measured with a model “UPA-UT151”available from Nikkiso Co., Ltd. (the same applies to the examplesbelow).

As the water-soluble polymer P1, was used a polyvinyl alcohol having adegree of saponification of 73% and a weight average molecular weight(Mw) of 2.8×10⁴. The water-soluble polymer P1 is a copolymer comprising73% by mole of polyvinyl alcohol units and 27% of vinyl acetate units.

Example B2

In this example, as the abrasive, was used a colloidal silica of 25 nmaverage primary particle diameter and 46 nm average secondary particlediameter. To a basic abrasive dispersion with approximately 0.18% NVformed of the abrasive, ammonia and ultrapure water, was added and mixedan aqueous polymer solution containing 1.5% by mass of water-solublepolymer P1 to prepare a polishing composition having 0.18% abrasive,0.005% ammonia and 0.010% water-soluble polymer HA with the reset beingwater. The polishing liquid had a pH of 10.1.

The concentrations of water-soluble polymer P1 and ammonia in thepolishing composition of this example were adjusted so that thewater-soluble polymer and ammonia contents relative to the surface areaof the abrasive in the unit volume of the polishing liquid wereapproximately equal to those in the polishing liquid of Example B1.

Example B3

In this example, in place of water-soluble polymer P1 in Example B1, wasused a polyvinyl alcohol (water-soluble polymer P2) having a degree ofsaponification of 79% by mole and a Mw of 2.7×10⁴. Otherwise, in thesame manner as Example B1, a polishing composition according to thisexample was prepared.

Example B4

In this example, in place of water-soluble polymer P1 in Example B1, wasused a polyvinyl alcohol (water-soluble polymer P3) comprising 80% bymole of polyvinyl alcohol units and 20% by mole of vinyl hexanoate unitsand having a Mw of 2.8×10⁴. Otherwise, in the same manner as Example B1,a polishing composition according to this example was prepared.

Example B5

In this example, in place of water-soluble polymer P1 in Example B1, wasused a polyvinyl alcohol (water-soluble polymer P4) comprising 80% bymole of polyvinyl alcohol units and 20% by mole of vinyl hexanoate unitsand having a Mw of 0.3×10⁴. The water-soluble polymer P4 concentrationin the polishing composition was 0.003%. Otherwise, in the same manneras Example B1, a polishing composition according to this example wasprepared.

Comparative Example B1

In this example, in place of water-soluble polymer P1 in Example B1, wasused a fully-saponified polyvinyl alcohol (polyvinyl alcohol having adegree of saponification 98% by mole and a Mw of 2.2×10⁴, water-solublepolymer P5, hereinafter). Otherwise, in the same manner as Example B1, apolishing composition according to this example was prepared.

Comparative Example B2

In this example, in place of water-soluble polymer P1 in Example B1, wasused a poly(N-vinylpyrrolidone) (water-soluble polymer P6) having a Mwof 6.0×10⁴. Otherwise, in the same manner as Example B1, a polishingcomposition according to this example was prepared.

Comparative Example B3

In this example, in place of water-soluble polymer P1 in Example B1, wasused a hydroxyethyl cellulose (water-soluble polymer P7) having a Mw of25×10⁴. Otherwise, in the same manner as Example B1, a polishingcomposition according to this example was prepared.

Comparative Example B4

In this example, in place of water-soluble polymer P1 in Example B1, wasused a graft copolymer (water-soluble polymer P8) obtained by graftingpolyvinyl alcohol with poly(N-vinylpyrrolidone). The graft copolymer hasan overall Mw of 17.5×10⁴. The polyvinyl alcohol chain in a singlemolecule of the graft copolymer has a Mw of 7.5×10⁴. Thepoly(N-pyrrolidone) chains has a combined Mw of 10×10⁴. The polyvinylalcohol chain had a degree of saponification of 98% by mole or greater.Otherwise, in the same manner as Example B1, a polishing compositionaccording to this example was prepared.

<Etching Rate Measurement>

With ultrapure water, were mixed an aqueous polymer solution comprising1.5% by mass of water-soluble polymer P1 used in Examples B1 and B2 andammonia water (29%) to prepare an etching rate measuring reagent LEcontaining 0.18% water-soluble polymer P1 and 1.3% ammonia with the restbeing water.

A 6 cm long by 3 cm wide by 775 μm thick rectangular silicon substrate(conductivity: p-type, crystal orientation: <100>) was obtained andimmersed in an aqueous hydrogen fluoride (3%) solution for one minute toremove the natural oxide film from the surface. Subsequently, thesilicon substrate was measured for its mass W0.

The silicon substrate was immersed in the reagent LE at room temperature(25° C.) for 12 hours, then removed from the reagent LE, and immersed ina cleaning solution containing NH₃(29%)/H₂O₂(31%)/ultrapure water at1/1/8 (volume ratio) at room temperature (25° C.) for 10 seconds. Thesilicon substrate removed from the cleaning solution was washed withwater and measured for its mass W1. From the difference between W0 andW1, the specific gravity (2.33 g/cm³) and surface area (18 cm²) of thesilicon substrate, the etching rate was found to be 0.8 nm/min.

With respect to the water-soluble polymers P2 to P8 used in the otherExamples and Comparative Examples, the etching rates were measured inthe same manner. The obtained results are shown in Table 4,corresponding to the Examples and Comparative Examples using therespective water-soluble polymers.

<Abrasive Adsorption Measurement>

The polishing composition according to Example B1 was centrifuged at arotational speed of 20000 rpm for 30 minutes, using a centrifuge undermodel name “AVANTI HP-30I” available from Beckman Coulter, Inc. Thecentrifuged supernatant was collected and subjected to measurement oftotal organic carbon (TOC), using a TOC analyzer (combustion catalyticoxidation method, model name “TOC-5000A”) available from ShimadzuCorporation. The measurement result was converted based on the volume ofthe supernatant to the total amount of organic carbon C1 (the totalamount of organic carbon of the water-soluble polymer contained as freepolymer in the supernatant). The time from the preparation of thepolishing composition to the start of centrifugation was approximatelyone hour.

A test solution L0 was prepared, having the same composition as that ofthe polishing composition but without the abrasive. In particular, thetest solution L0 was prepared to have 0.010% ammonia (NH₃) and 0.018%water-soluble polymer P1 with the rest being water. The test solution L0was measured for TOC with the TOC analyzer and converted to thevolume-based value to determine the total amount of organic carbon C0 inthe test solution L0.

From the C0 and C1, based on the following equation:Abrasive adsorption (%)=[(C0−C1)/C0]×100the abrasive adsorption was found to be almost 0%.

The polishing compositions according to Examples B2 to B5 andComparative Examples B1 to B4 were also measured for their abrasiveadsorption in the same manner. The obtained results are shown in Table4.

<Silicon Wafer Polishing>

Using the polishing compositions according to the respective examples asthey were as polishing liquids, silicon wafer surfaces were polishedunder the conditions shown below. The silicon wafers used had 300 mmdiameter, p-type conductivity, crystal orientation of <100> and aresistivity of 0.1 Ω·cm or greater, but less than 100 Ω·cm, and werepreliminarily polished with a polishing slurry (trade name “GLANZOX2100” available from Fujimi, Inc.) to a surface roughness of 0.1 nm to10 nm for the use. The time from the preparation of the polishingcomposition to the start of polishing was about one hour.

[Polishing Conditions]

Polishing machine: Sheet-type polisher with model number “PNX-332B”available from Okamoto Machine Tool Works, Ltd.

Polishing tables: Using two rear tables among three tables of thepolishing machine, the first and second stages of final polishing afterthe preliminary polishing were carried out.

(The conditions below were common between the two tables)

Polishing pressure: 15 kPa

Plate rotational speed: 30 rpm

Head rotational speed: 30 rpm

Polishing time: 2 min

Temperature of polishing liquid: 20° C.

Flow rate of polishing liquid: 2.0 L/min (drain)

<Cleaning>

Polished silicon wafers were cleaned (SC-1 cleaned) with a cleaningsolution at NH₄OH (29%)/H₂O₂(31%)/deionized water (DIW)=1/3/30 (volumeratio). More specifically, two cleaning baths each equipped with anultrasonic wave oscillator of 950 kHz frequency were obtained; thecleaning solution was placed in each of the first and second cleaningbaths and maintained at 60° C.; and each polished silicon wafer wasimmersed in the first cleaning bath for 6 minutes and then, via aultrasonic rinsing bath with ultrapure water, in the second cleaningbath for 6 minutes, with the respective ultrasonic wave oscillatorsturned on.

<Counting of the number of micro particles (LPD)>

Using a wafer inspection system under trade name “SURFSCAN SP2”available from KLA-Tencor Corporation, the number of 37 nm or largerparticles (number of LPD) present on each cleaned silicon wafer of 300mm diameter was counted.

<Haze Measurement>

The surface of each cleaned silicon wafer was measured for haze (ppm) inDWO mode, using a wafer inspection system under trade name “SURFSCANSP2” available from KLA-Tencor Corporation.

The results of the LPD count and haze measurement are converted torelative values and shown in Table 4, with 100% being the number of LPDand haze value of Comparative Example B1 using solely thefully-saponified polyvinyl alcohol (PVA) as the water-soluble polymer.In the column for the LPD count of Table 4, “n/m” (not measured)indicates that the defect analysis with the wafer inspection systemresulted in data overload, that is, the number of LPD exceeded the uppermeasurement limit.

<Evaluation of Ease of Filtration>

The polishing liquid according to each example was filtered by suctionat a temperature of 25° C. at a filter differential pressure of 50 kPa.As the filter, was used a disc filter under trade name “ULTIPOR® N66”(47 mm diameter, rated filter resolution of 0.2 g/nm). From the volumeof the polishing composition that passed through the filter until theflow of the polishing composition passing through the filter stopped,the ease of filtration was evaluated in the two grades below. Theobtained results are shown in the column headed “Ease of Filtration” inTable 4.

A: The volume of the polishing composition that passed through thefilter was 25 mL or greater.

C: The volume of the polishing composition that passed through thefilter was less than 25 mL.

TABLE 4 Abrasive Average primary Water-soluble adsorption Etching rateparticle diameter Haze LPD Ease of polymer (%) (nm/min) (nm) (%) (%)filtration Ex. B1 P1 0 0.8 35 36 40 A Ex. B2 P1 0 0.8 25 31 40 A Ex. B3P2 0 0.9 35 38 43 A Ex. B4 P3 0 0.8 35 40 40 A Ex. B5 P4 0 0.8 35 36 40A Comp. Ex. B1 P5 0 2.8 35 100 100  A Comp. Ex. B2 P6 90 1.0 35 178 n/mA Comp. Ex. B3 P7 51 3.4 35 44 50 C Comp. Ex. B4 P8 51 2.0 35 67 65 CP1: Vinyl alcohol(73 mol. %)-Vinyl acetate(27 mol. %) copolymer; Mw 2.8× 10⁴ P2: Vinyl alcohol(79 mol. %)-Vinyl acetate(21 mol. %)copolymer; Mw2.7 × 10⁴ P3: Vinyl alcohol(80 mol. %)-Vinyl hexanoate(20 mol.%)copolymer; Mw 2.8 × 10⁴ P4: Vinyl alcohol(80 mol. %)-Vinylhexanoate(20 mol. %) copolymer; Mw 0.3 × 10⁴ P5: Vinyl alcohol(98 mol.%)-Vinyl acetate(2 mol. %) copolymer; Mw 2.2 × 10⁴ P6:Polyvinylpyrrolidone; Mw 6.0 × 10⁴ P7: Hydroxyethyl cellulose; Mw 25 ×10⁴ P8: Polyvinyl alcohol(Mw 7.5 × 10⁴) -Polyvinylpyrrolidone(Mw 10 ×10⁴) graft copolymer

As shown in Table 4, with respect to the polishing composition ofComparative Example B1 using the fully-saponified PVA as thewater-soluble polymer, while the abrasive adsorption was at or below20%, the etching rate was higher than 2.0 nm/min, showing its poorability to protect surfaces. Thus, when compared with ComparativeExample B3 using HEC, while it showed greater ease of filtration, itshaze clearly increased.

On the contrary, according to the polishing liquids of Examples B1 toB5-satisfying both the abrasive adsorption being 20% or lower and theetching rate being 2.0 nm/min or lower, while the filtration was as easyas Comparative Example B1, the haze value and the LPD count weresignificantly lower in comparison to Comparative Example B1. Accordingto the polishing compositions of Examples B1 to B5, the haze value andthe LPD count were further reduced even in comparison to ComparativeExample B3.

On the other hand, the polishing liquid of Comparative Example B2-whichshowed a low etching rate, but a high abrasive adsorption—was poorlyeffective in both haze reduction and LPD count reduction. An explanationto this could be that the excessively high abrasive adsorption broughtabout shortage of free polymer, resulting in insufficient surfaceprotection effect. Comparative Example B3 and Comparative Example B4having an abrasive adsorption similar to the first were both inferior toExamples B1 to B5 in both the haze value reduction effect and LPD countreduction effect.

Experiment 3

<Preparation of Polishing Compositions>

Example C1

Were obtained a basic abrasive dispersion (agent A) formed of 12%abrasive and 0.26% (0.16 mol/L) ammonia with the reset being water andan aqueous polymer solution (agent B) comprising 1.5% of a water-solublepolymer.

As the abrasive, was used a colloidal silica (abrasive GA) of 35 nmaverage primary particle diameter and 66 nm average secondary particlediameter. The average primary particle diameter was measured with asurface area analyzer under trade name “FLOW SORB 112300” available fromMicromeritics. The average secondary particle diameter was the volumeaverage secondary particle diameter measured with a model “UPA-UT151”available from Nikkiso Co., Ltd. (the same applies to the examplesbelow).

As the water-soluble polymer P1, was used a polyvinyl alcohol(water-soluble polymer HA) having a degree of saponification of 73% bymole and a weight average molecular weight (Mw) of 2.8×10⁴. Thewater-soluble polymer HA has a molecular structure comprising 27% bymole of vinyl acetate units as an acetoxy group-containing repeat unit.

808 g of the agent A was diluted with 19000 g of ultrapure water toprepare a first composition containing about 0.49% abrasive and 0.006mol/L ammonia. To the first composition (diluted agent A), was added andmixed 246 g of the agent B to prepare a polishing composition (pH 10.2)containing 0.48% abrasive GA, 0.010% (0.006 mol/L) ammonia and 0.018%water-soluble polymer HA with the rest being water. The polishingcomposition was stirred at room temperature for about one hour and thenused for polishing a silicon wafer described later.

Example C2

Were obtained a basic abrasive dispersion (agent A) containing 9.4%abrasive GA and 0.20% (0.12 mol/L) ammonia with the rest being water andan aqueous polymer solution (agent B) containing 15% of a water-solublepolymer.

As the water-soluble polymer, was used a polyvinyl alcohol(water-soluble polymer HB) having a degree of saponification of 79% bymole and a Mw of 2.7×10⁴. The water-soluble polymer HB has a molecularstructure comprising 21% by mole of vinyl acetate units. 1030 g of theagent A was diluted with 19000 g of ultrapure water to prepare a firstcomposition containing about 0.48% abrasive and 0.006 mol/L ammonia. Tothe first composition (diluted agent A), was added and mixed 25 g of theagent B to prepare a polishing composition (pH 10.2) containing 0.48%abrasive GA, 0.010% (0.006 mol/L) ammonia and 0.019% water-solublepolymer HB with the rest being water. The polishing composition wasstirred at room temperature for about one hour and then used forpolishing a silicon wafer described later.

Example C3

Were obtained a basic abrasive dispersion (agent A) containing 19.2%abrasive GA and 0.41% (0.28 mol/L) ammonia with the rest being water andan aqueous polymer solution (agent B) containing 15% water-solublepolymer HB.

1005 g of the agent A was diluted with 39000 g of ultrapure water toprepare a first composition containing about 0.48% abrasive and 0.006mol/L ammonia. To the first composition (diluted agent A), was added andmixed 49 g of the agent B to prepare a polishing composition (pH 10.2)containing 0.48% abrasive GA, 0.010% (0.006 mol/L) ammonia and 0.019%water-soluble polymer HB with the rest being water. The polishingcomposition was stirred at room temperature for about one hour and thenused for polishing a silicon wafer described later.

Example C4

Were obtained a basic abrasive dispersion (agent A) containing 5.2%abrasive and 0.11% (0.067 mol/L) ammonia with the rest being water andan aqueous polymer solution (agent B) containing 1.5% water-solublepolymer HA.

As the abrasive, was used a colloidal silica (abrasive GB) of 25 nmaverage primary particle diameter and 46 nm average secondary particlediameter.

532 g of the agent A was diluted with 19000 g of ultrapure water toprepare a first composition containing about 0.18% abrasive and 0.002mol/L ammonia. To the first composition (diluted agent A), was added andmixed 123 g of the agent B to prepare a polishing composition (pH 10.2)containing 0.18% abrasive GB, 0.003% (0.002 mol/L) ammonia and 0.009%water-soluble polymer HA with the rest being water. The polishingcomposition was stirred at room temperature for about one hour and thenused for polishing a silicon wafer described later.

The concentrations of water-soluble polymer HA and ammonia in thepolishing composition of this example were adjusted so that thewater-soluble polymer HA and ammonia contents relative to the surfacearea of the abrasive in the unit volume of the polishing compositionwere approximately equal to those in the polishing composition ofExample C1.

Comparative Example C1

A concentrate was prepared, containing 9.2% abrasive GA, 0.20% (0.12mol/L) ammonia and 0.35% water-soluble polymer HA with the rest beingwater.

At 24 hours after the preparation of the concentrate, 1055 g of theconcentrate was diluted with 19000 g of ultrapure water to prepare apolishing composition (pH 10.2) containing 0.48% abrasive GA, 0.010%(0.006 mol/L) ammonia and 0.018% water-soluble polymer HA with the restbeing water. The polishing composition was stirred at room temperaturefor about one hour and then used for polishing a silicon wafer describedlater.

Comparative Example C2

In this example, in place of water-soluble polymer HA in Example C1, wasused a fully-saponified polyvinyl alcohol (polyvinyl alcohol having adegree of saponification 98% by mole and a Mw 2.2×10⁴, “PVA”hereinafter). Otherwise, in the same manner as Example C1, was prepareda polishing composition (pH 10.2) containing 0.48% abrasive GA, 0.010%(0.006 mol/L) ammonia and 0.018% PVA with the rest being water. Thepolishing composition was stirred at room temperature for about one hourand then used for polishing a silicon wafer described later.

Comparative Example C3

In this example, in place of water-soluble polymer HB in Example C2, wasused a poly(N-vinylpyrrolidone) with a Mw of 6×10⁴ (or “PVP”hereinafter). Otherwise, in the same manner as Example C2, was prepareda polishing composition (pH 10.2) containing 0.48% abrasive GA, 0.010%(0.006 mol/L) ammonia and 0.019% PVP with the rest being water. Thepolishing composition was stirred at room temperature for about one hourand then used for polishing a silicon wafer described later.

Comparative Example C4

A concentrate was prepared, containing 9.2% abrasive GA, 0.2% (0.12mol/L) ammonia and 0.35% water-soluble polymer with the rest beingwater.

As the water-soluble polymer, was used a hydroxyethyl cellulose with aMw of 25×10⁴ (or “HEC” hereinafter).

At 24 hours after the preparation of the concentrate, 1055 g of theconcentrate was diluted with 19000 g of ultrapure water to prepare apolishing composition (pH 10.2) containing 0.48% abrasive GA, 0.010%(0.006 mol/L) ammonia and 0.018% HEC with the rest being water. Thepolishing composition was stirred at room temperature for about one hourand then used for polishing a silicon wafer described later.

<Silicon Wafer Polishing>

Using the polishing compositions according to the respective examples asthey were as polishing liquids, silicon wafer surfaces were polishedunder the conditions shown below. The silicon wafers used had 300 mmdiameter, p-type conductivity, crystal orientation of <100> and aresistivity of 0.1 Ω·cm or greater, but less than 100 Ω·cm, and werepreliminarily polished with a polishing slurry (trade name “GLANZOX2100” available from Fujimi, Inc.) to a surface roughness of 0.1 nm to10 nm for the use.

[Polishing Conditions]

Polishing machine: Sheet-type polisher with model number “PNX-332B”available from Okamoto Machine Tool Works, Ltd.

Polishing tables: Using two rear tables among three tables of thepolishing machine, the first and second stages of final polishing afterthe preliminary polishing were carried out.

(The conditions below were common between the two tables)

Polishing pressure: 15 kPa

Plate rotational speed: 30 rpm

Head rotational speed: 30 rpm

Polishing time: 2 min

Temperature of polishing liquid: 20° C.

Flow rate of polishing liquid: 2.0 L/min (drain)

<Cleaning>

Polished silicon wafers were cleaned (SC-1 cleaned) with a cleaningsolution at NH₄OH (29%)/H₂O₂(31%)/deionized water (DIW)=1/3/30 (volumeratio). More specifically, two cleaning baths each equipped with anultrasonic wave oscillator of 950 kHz frequency were obtained; thecleaning solution was placed in each of the first and second cleaningbaths and maintained at 60° C.; and each polished silicon wafer wasimmersed in the first cleaning bath for 6 minutes and then, via aultrasonic rinsing bath with ultrapure water, in the second cleaningbath for 6 minutes, with the respective ultrasonic wave oscillatorsturned on.

<Assessment of the number of micro particles (LPD)>

Using a wafer inspection system under trade name “SURFSCAN SP2”available from KLA-Tencor Corporation, the number of 37 nm or largerparticles (number of LPD) present on each cleaned silicon wafer of 300mm diameter was counted.

<Haze Measurement>

The surface of each cleaned silicon wafer was measured for haze (ppm) inDWO mode, using a wafer inspection system under trade name “SURFSCANSP2” available from KLA-Tencor Corporation.

The results of the LPD count and haze measurement are converted torelative values and shown in Table 5, with 100% being the number of LPDand haze value of Comparative Example C4 using solely the hydroxyethylcellulose (HEC) as the water-soluble polymer. In the column for thenumber of LPD of Table 5, “n/m” (not measured) indicates that the defectanalysis with the wafer inspection system resulted in data overload,that is, the number of LPD exceeded the upper measurement limit.

<Evaluation of Ease of Filtration>

The polishing liquid according to each example was filtered by suctionat a temperature of 25° C. at a filter differential pressure of 50 kPa.As the filter, was used a disc filter under trade name “ULTIPOR® N66”(47 mm diameter, rated filter resolution of 0.2 μm). From the volume ofthe polishing composition that passed through the filter until the flowof the polishing composition passing through the filter stopped, theease of filtration was evaluated in the two grades below. The obtainedresults are shown in the column headed “Ease of Filtration” in Table 5.

A: The volume of the polishing composition that passed through thefilter was 25 mL or greater.

C: The volume of the polishing composition that passed through thefilter was less than 25 mL.

TABLE 5 Water-soluble polymer (deg. Haze LPD Ease of Abrasive of sap.)Procedures of preparation (%) (%) filtration Ex. C1 GA HA I. Agent A (12mass % abrasive, 0.16 mol/L NH₃) 80 60 A (73 mol %) was diluted to 0.49mass % abrasive, 0.006 mol/L NH₃ II. Agent B containing water-solublepolymer was added to the dilution to prepare a mixture of 0.48 mass %abrasive, 0.006 mol/L NH₃ Ex. C2 GA HB I. Agent A (9.4 mass % abrasive,0.12 mol/L NH₃) 85 65 A (79 mol %) was diluted to 0.48 mass % abrasive,0.006 mol/L NH₃ II. Agent B containing water-soluble polymer was addedto the dilution to prepare a mixture of 0.48 mass % abrasive, 0.006mol/L NH₃ Ex. C3 GA HB I. Agent A (19.2 mass % abrasive, 0.28 mol/L NH₃)85 60 A (79 mol %) was diluted to 0.48 mass % abrasive, 0.006 mol/L NH₃II. Agent B containing water-soluble polymer was added to the dilutionto prepare a mixture of 0.48 mass % abrasive, 0.006 mol/L NH₃ Ex. C4 GBHA I. Agent A (5.2 mass % abrasive, 0.067 mol/L NH₃) 70 50 A (73 mol %)was diluted to 0.18 mass % abrasive, 0.002 mol/L NH₃ II. Agent Bcontaining water-soluble polymer was added to the dilution to prepare amixture of 0.18 mass % abrasive, 0.002 mol/L NH₃ Comp. GA HA Concentratecontaining water-soluble polymer (9.2 210 200 A Ex. C1 (73 mol %) mass %abrasive, 0.12 mol/L NH₃) was diluted to a mixture of 0.48 mass %abrasive, 0.006 mol/L NH₃ Comp. GA PVA I. Agent A (12 mass % abrasive,0.16 mol/L NH₃) 225 200 A Ex. C2 was diluted to 0.49 mass % abrasive,0.006 mol/L NH₃ II. Agent B containing water-soluble polymer was addedto the dilution to prepare a mixture of 0.48 mass % abrasive, 0.006mol/L NH₃ Comp. GA PVP I. Agent A (9.4 mass % abrasive, 0.12 mol/L NH₃)400 n/m A Ex. C3 was diluted to 0.48 mass % abrasive, 0.006 mol/L NH₃II. Agent B containing water-soluble polymer was added to the dilutionto prepare a mixture of 0.48 mass % abrasive, 0.006 mol/L NH₃ Comp. GAHEC Concentrate containing water-soluble polymer (9.2 100 100 C Ex. C4mass % abrasive, 0.12 mol/L NH₃) was diluted to prepare a mixture of0.48 mass % abrasive, 0.006 mol/L NH₃

As shown in Table 5, the polishing composition of Example C1-produced bydiluting the agent A containing the abrasive and basic compound tosatisfy at least either the abrasive concentration being lower than 3%by mass or the ammonia concentration being 0.1 mol/L or lower, followedby adding the aqueous water-soluble polymer HA solution to the resultingdilution—was superior in terms of both the haze value and LPD count incomparison to the polishing composition of Comparative Example C1produced by diluting the concentrate comprising the basic compound andwater-soluble polymer HA together. The polishing composition of ExampleC1 was also more effective in reducing the haze value and LPD count whencompared against Comparative Example C4 using a widely-usedwater-soluble polymer, HEC. In addition, it was clearly superior toComparative Example C4 in terms of the ease of filtration as well. Thepolishing compositions of Examples C2 to C4 produced in the same manneras Example C1 were also highly effective in reducing the haze value andLPD count and easily filtered as well.

On the other hand, the polishing composition of Comparative ExampleC2-using PVA comprising vinyl alcohol units similarly to water-solublepolymers HA and HB, but being essentially free of vinyl acetateunits—was produced in the same manner as Examples C1 to C4, but did notproduce the effect to reduce the haze value and LPD count as Examples C1to C4 did. The polishing composition of Comparative Example C3 producedwith PVP (an ester bond-free water-soluble polymer) in the same manneras Examples C1 to C4 also fell short of Examples C1 to C4 in terms ofthe haze value and LPD count.

It is noted that in Examples C1 to C4, after the preparation, thepolishing compositions were stored at room temperature for about onehour until used for polishing; however, even when the storage time waschanged to 12 hours or 48 hours, in comparison to Comparative ExamplesC1 to C4, the effects were comparable to the results shown in Table 5.

Just before the respective polishing compositions of Examples C1 to C4were put in use for polishing, the ratios of numbers of moles of vinylacetate units to numbers of moles of all monomeric repeat unitsconstituting the water-soluble polymers in the respective polishingcompositions were determined and found to be 25% in Example C1, 19% inExample C2, 19% in Example C3 and 16% in Example C4. In other words, thepolishing compositions according to Examples C1 to C4 were found tocontain a water-soluble polymer (polyvinyl alcohol with a degree ofsaponification of 95% by mole or lower) with the molar ratio of vinylacetate units being maintained at or above 5%.

The molar ratios were determined as follows: The abrasive in thepolishing composition was precipitated by centrifugation; While a basiccompound was added to the resulting supernatant as a sample solution andthe resultant was heated to complete saponification, the amount of basiccompound consumed was titrated; From the result, the number of moles ofvinyl carboxylate units and the number of moles of vinyl alcohol unitswere determined.

Experiment 4

<Preparation of Polishing Compositions>

Example D1

As the agent A, was obtained a basic abrasive dispersion (agent A1)comprising 12% abrasive and 0.26% (0.16 mol/L) ammonia with the restbeing water. As the abrasive, was used a colloidal silica (abrasive GA)of 35 nm average primary particle diameter and 66 nm average secondaryparticle diameter. The average primary particle diameter was measuredwith a surface area analyzer under trade name “FLOW SORB 112300”available from Micromeritics. The average secondary particle diameterwas the volume average secondary particle diameter measured with a model“UPA-UT151” available from Nikkiso Co., Ltd. (the same applies to theexamples below).

As the agent B, was obtained an aqueous polymer solution (agent B1)containing 1.5% of a water-soluble polymer. As the water-solublepolymer, was used a polyvinyl alcohol (water-soluble polymer HA) havinga degree of saponification of 73% and a weight average molecular weight(Mw) of 2.8×10⁴. The water-soluble polymer HA has a molecular structurecomprising 27% by mole of vinyl acetate units as an acetoxygroup-containing repeat unit.

To 808 g of the agent A1, was added 246 g of the agent B1 to prepare apolishing composition stock solution containing 9.2% abrasive and 0.12mol/L ammonia. At one minute after the preparation of the stock solution(i.e. at one minute after the agents A1 and B1 were mixed), ultrapurewater was added to dilute the stock solution by a factor of 20 by volumeto prepare a polishing composition (pH 10.2) containing 0.46% abrasiveand 0.006 mol/L ammonia.

Example D2

As the agent A, was obtained a basic abrasive dispersion (agent A2)comprising 9.4% abrasive GA and 0.20% (0.12 mol/L) ammonia with the restbeing water.

As the agent B, was obtained an aqueous polymer solution (agent B2)containing 15% of a water-soluble polymer. As the water-soluble polymer,was used a polyvinyl alcohol (water-soluble polymer HB) having a degreeof saponification of 79% by mole and a Mw of 2.7×10⁴. The water-solublepolymer HB has a molecular structure comprising 21% by mole of vinylacetate units.

To 1030 g of the agent A2, was added 25 g of the agent B2 to prepare apolishing composition stock solution containing 9.2% abrasive and 0.12mol/L ammonia. At one hour after the preparation of the stock solution,ultrapure water was added to dilute the stock solution by a factor of 20by volume to prepare a polishing composition (pH 10.2) containing 0.46%abrasive and 0.006 mol/L ammonia.

Example D3

In Example D1, the time from the preparation of the polishingcomposition to the dilution with ultrapure water was changed to 6 hours.Otherwise, in the same manner as Example D1, a polishing compositionaccording to this example was prepared.

Example D4

As the agent A, was obtained a basic abrasive dispersion (agent A3)comprising 19.2% abrasive GA and 0.41% (0.28 mol/L) ammonia with therest being water.

As the agent B, was obtained an aqueous polymer solution (agent B2)containing 15% of a water-soluble polymer. As the water-soluble polymer,was used a polyvinyl alcohol (water-soluble polymer HIB) having a degreeof saponification of 79% by mole and a Mw of 2.7×10⁴. The water-solublepolymer HB has a molecular structure comprising 21% by mole of vinylacetate units.

To 1005 g of the agent A3, was added 49 g of the agent B2 to prepare apolishing composition stock solution containing 18.3% abrasive and 0.24mol/L ammonia. At 12 hours after the preparation of the stock solution,ultrapure water was added to dilute the stock solution by a factor of 40by volume to prepare a polishing composition (pH 10.2) containing 0.46%abrasive and 0.006 mol/L ammonia.

Example D5

As the agent A, was obtained a basic abrasive dispersion (agent A4)comprising 4.4% abrasive and 0.11% (0.067 mol/L) ammonia with the restbeing water. As the abrasive, was used a colloidal silica (abrasive GB)of 25 nm average primary particle diameter and 46 nm average secondaryparticle diameter.

As the agent B, was used an aqueous polymer solution (agent B1)containing 1.5% water-soluble polymer HA.

To 532 g of the agent A4, was added 123 g of the agent B1 to prepare apolishing composition stock solution containing 3.6% abrasive and 0.055mol/L ammonia. At 20 hours after the preparation of the stock solution,ultrapure water was added to dilute the stock solution by a factor of 20by volume to prepare a polishing composition (pH 10.2) containing 0.18%abrasive and 0.003 mol/L ammonia.

Comparative Example D1

In Example D1, the time from the preparation of the polishingcomposition to the dilution with ultrapure water was changed to 30hours. Otherwise, in the same manner as Example D1, a polishingcomposition (0.46% abrasive, 0.006 mol/L ammonia) according to thisexample was prepared.

Comparative Example D2

In Example D2, the time from the preparation of the polishingcomposition to the dilution with ultrapure water was changed to 64hours. Otherwise, in the same manner as Example D1, a polishingcomposition (0.46% abrasive, 0.006 mol/L ammonia) according to thisexample was prepared.

Comparative Example D3

In this example, as the agent B, was used an aqueous polymer solution(agent B3) containing 1.5% of a fully-saponified polyvinyl alcohol(polyvinyl alcohol having a degree of saponification of 98% by mole anda Mw of 2.2×10⁴, “PVA” hereinafter).

To 808 g of the agent A1, was added 246 g of the agent B3 to prepare apolishing composition stock solution containing 9.2% abrasive and 0.12mol/L ammonia. At one minute after the preparation of the stocksolution, ultrapure water was added to dilute the stock solution by afactor of 20 by volume to prepare a polishing composition (pH 10.2)containing 0.46% abrasive and 0.006 mol/L ammonia.

Comparative Example D4

In this example, as the agent B, was used an aqueous polymer solution(agent B4) containing 1.5% of a poly(N-vinylpyrrolidone with a Mw of6×10⁴ (or “PVP” hereinafter).

To 808 g of the agent A1, was added 246 g of the agent B4 to prepare apolishing composition stock solution containing 9.2% abrasive and 0.12mol/L ammonia. At 6 hours after the preparation of the stock solution,ultrapure water was added to dilute the stock solution by a factor of 20by volume to prepare a polishing composition (pH 10.2) containing 0.46%abrasive and 0.006 mol/L ammonia.

Comparative Example D5

In this example, as the agent B, was used an aqueous polymer solution(agent B5) containing 1.5% of a hydroxyethyl cellulose with a Mw of25×10⁴ (or “HEC” hereinafter).

To 808 g of the agent A1, was added 246 g of the agent B5 to prepare apolishing composition stock solution containing 9.2% abrasive and 0.12mol/L ammonia. At 6 hours after the preparation of the stock solution,ultrapure water was added to dilute the stock solution by a factor of 20by volume to prepare a polishing composition (pH 10.2) containing 0.46%abrasive and 0.006 mol/L ammonia.

<Silicon Wafer Polishing>

The polishing compositions thus prepared according to Examples D1 to D5and Comparative Examples D1 to D5 were stored with stirring at roomtemperature for about one hour. Subsequently, using the polishingcompositions according to the respective examples as they were aspolishing liquids, silicon wafer surfaces were polished under theconditions shown below. The silicon wafers used had 300 mm diameter,p-type conductivity, crystal orientation of <100> and a resistivity of0.1 Ω·cm or greater, but less than 100 Ω·cm, and were preliminarilypolished with a polishing slurry (trade name “GLANZOX 2100” availablefrom Fujimi, Inc.) to a surface roughness of 0.1 nm to 10 nm for theuse.

[Polishing Conditions]

Polishing machine: Sheet-type polisher with model number “PNX-332B”available from Okamoto Machine Tool Works, Ltd.

Polishing tables: Using two rear tables among three tables of thepolishing machine, the first and second stages of final polishing afterthe preliminary polishing were carried out.

(The conditions below were common between the two tables)

Polishing pressure: 15 kPa

Plate rotational speed: 30 rpm

Head rotational speed: 30 rpm

Polishing time: 2 min

Temperature of polishing liquid: 20° C.

Flow rate of polishing liquid: 2.0 L/min (drain)

<Cleaning>

Polished silicon wafers were cleaned (SC-1 cleaned) with a cleaningsolution at NH₄OH (29%)/H₂O₂(31%)/deionized water (DIW)=1/3/30 (volumeratio). More specifically, two cleaning baths each equipped with anultrasonic wave oscillator of 950 kHz frequency were obtained; thecleaning solution was placed in each of the first and second cleaningbaths and maintained at 60° C.; and each polished silicon wafer wasimmersed in the first cleaning bath for 6 minutes and then, via aultrasonic rinsing bath with ultrapure water, in the second cleaningbath for 6 minutes, with the respective ultrasonic wave oscillatorsturned on.

<Assessment of the Number of Micro Particles (LPD)>

Using a wafer inspection system under trade name “SURFSCAN SP2”available from KLA-Tencor Corporation, the number of 37 nm or largerparticles (number of LPD) present on each cleaned silicon wafer of 300mm diameter was counted.

<Haze Measurement>

The surface of each cleaned silicon wafer was measured for haze (ppm) inDWO mode, using a wafer inspection system under trade name “SURFSCANSP2” available from KLA-Tencor Corporation.

The results of the LPD count and haze measurement are converted torelative values and shown in Table 6, with 100% being the number of LPDand haze value of Comparative Example D5 using solely the hydroxyethylcellulose (HEC) as the water-soluble polymer. In the column for thenumber of LPD of Table 6, “n/m” (not measured) indicates that the defectanalysis with the wafer inspection system resulted in data overload,that is, the number of LPD exceeded the upper measurement limit.

<Evaluation of Ease of Filtration>

The polishing liquid according to each example was filtered by suctionat a temperature of 25° C. at a filter differential pressure of 50 kPa.As the filter, was used a disc filter under trade name “ULTIPOR® N66”(47 mm diameter, rated filter resolution of 0.2 μm). From the volume ofthe polishing composition that passed through the filter until the flowof the polishing composition passing through the filter stopped, theease of filtration was evaluated in the two grades below. The obtainedresults are shown in the column headed “Ease of Filtration” in Table 6.

A: The volume of the polishing composition that passed through thefilter was 25 mL or greater.

C: The volume of the polishing composition that passed through thefilter was less than 25 mL.

TABLE 6 Time from Agent B preparation of Abrasive content (wt %) Conc.of NH₃ (mol/L) Agent A (Water-soluble stock solution Stock PolishingStock Polishing Haze LPD Ease of (Abrasive) polymer) to dilutionsolution composition solution composition (%) (%) filtration Ex. D1 A1B1 1 min 9.2 0.46 0.12 0.006 80 60 A (GA) (HA; deg. of sap. 73 mol %)Ex. D2 A2 B2 1 h 9.2 0.46 0.12 0.006 85 65 A (GA) (HB; deg. of sap. 79mol %) Ex. D3 A1 B1 6 h 9.2 0.46 0.12 0.006 85 65 A (GA) (HA; deg. ofsap. 73 mol %) Ex. D4 A3 B2 12 h 18.3 0.46 0.24 0.006 90 70 A (GA) (HB;deg. of sap. 79 mol %) Ex. D5 A4 B1 20 h 3.6 0.18 0.055 0.003 85 70 A(GB) (HA; deg. of sap. 73 mol %) Comp. A1 B1 30 h 9.2 0.46 0.12 0.006210 200 A Ex. D1 (GA) (HA; deg. of sap. 73 mol %) Comp. A2 B2 64 h 9.20.46 0.12 0.006 230 210 A Ex. D2 (GA) (HB; deg. of sap. 79 mol %) Comp.A1 B3 1 min 9.2 0.46 0.12 0.006 225 200 A Ex. D3 (GA) (PVA) Comp. A1 B46 h 9.2 0.46 0.12 0.006 400 n/m A Ex. D4 (GA) (PVP) Comp. A1 B5 6 h 9.20.46 0.12 0.006 100 100 C Ex. D5 (GA) (HEC)

As shown in Table 6, among Examples D1 to D5 and Comparative Examples D1to D2 each using a partially-saponified polyvinyl alcohol as thewater-soluble polymer H, the polishing compositions of Examples D1 toD5-produced with the time spent being 24 hours or less from thepreparation of the polishing composition stock solution to thedilution—were clearly superior in terms of both the haze value and LPDcount in comparison to Comparative Examples D1 to D2 wherein the timewas more than 24 hours. The polishing compositions of D1 to D5 showedgreater effect to reduce the haze value and LPD count even when comparedagainst Comparative Example D5 using HEC (a widely-used water-solublepolymer) and were also clearly superior to Comparative Example D5 interms of the ease of filtration as well.

In addition, in comparison of Example D2 with Example D4, it can be seenthat with the time from the stock solution preparation to the dilutionbeing 10 hours or less, as compared with a case where the dilution isperformed at 12 hours after the stock solution preparation, a polishingcomposition can be produced to provide higher performance in terms ofthe haze value and LPD count. Similar tendencies are apparent in the LPDcounts of Example D3 and Example D5.

On the other hand, the polishing composition of Comparative ExampleD3-using the PVA that comprised vinyl alcohol units similarly towater-soluble polymers HA and HB, but was essentially free of vinylacetate units—was produced with the time from the stock solutionpreparation to the dilution being one minute just like in Example D1,but did not produce the effect to reduce the haze value and LPD count asExample D1 did. The polishing composition of Comparative Example D4produced with PVP (an ester bond-free water-soluble polymer) in the samemanner as Examples D1 to D5 also fell short of Examples D1 to D5 interms of the haze value and LPD count.

It is noted that in Examples D1 to D5, after the preparation, thepolishing compositions were stored at room temperature for about onehour until used for polishing; however, even when the storage time waschanged to 12 hours or 48 hours, in comparison to Comparative ExamplesD1 to D5, the effects were comparable to the results shown in Table 6.

Just before the respective polishing compositions of Examples D1 to D5were put in use for polishing, the ratios of numbers of moles of vinylacetate units to numbers of moles of all monomeric repeat unitsconstituting the water-soluble polymers in the respective polishingcompositions were determined and found to be 27% in Example D1, 18% inExample D2, 15% in Example D3, 10% in Example D4 and 8% in Example D5.In other words, the polishing compositions according to Examples D1 toD5 were found to contain a water-soluble polymer (polyvinyl alcohol witha degree of saponification of 95% by mole or lower) with the molar ratioof vinyl acetate units being maintained at or above 5%.

The molar ratios were determined as follows: The abrasive in thepolishing composition was precipitated by centrifugation; While a basiccompound was added to the resulting supernatant as a sample solution andthe resultant was heated to complete saponification, the amount of basiccompound consumed was titrated; From the result, the number of moles ofvinyl carboxylate units and the number of moles of vinyl alcohol unitswere determined.

Although specific embodiments of the present invention have beendescribed in detail above, these are merely for illustrations and do notlimit the scope of claims. The art according to the claims includesvarious modifications and changes made to the specific embodimentsillustrated above.

What is claimed is:
 1. A polishing composition comprising: awater-soluble polymer; an abrasive; and water, wherein the water-solublepolymer has a repeat unit that does not have any hydroxyl groups, therepeat unit that does not have any hydroxyl groups is at least oneselected from the group consisting of a propylene oxide unit, anethylene oxide unit, an N-isopropylacrylamide unit, a vinyl hexanoateunit, and a butyl vinyl ether unit, the water-soluble polymer has ahydroxyl group content in a range of 4 mmol/g or higher and 21 mmol/g orlower, and the abrasive consists of silica particles.
 2. The compositionaccording to claim 1, wherein the water-soluble polymer is nonionic. 3.The composition according to claim 1, wherein the water-soluble polymerhas a repeat unit A that comprises a hydroxyl group.
 4. The compositionaccording to claim 3, wherein the water-soluble polymer has a vinylalcohol unit as the repeat unit A.
 5. The composition according to claim1, wherein the repeat unit that does not have any hydroxyl groups is atleast one selected from the group consisting of a propylene oxide unit,an ethylene oxide unit, an N-isopropylacrylamide unit and a vinylhexanoate unit.
 6. The composition according to claim 1, wherein thewater-soluble polymer has a weight average molecular weight of 1×10⁴ orhigher.
 7. The composition according to claim 1, wherein a pH is 9.0 ormore and 12.0 or less.
 8. The composition according to claim 1, whereinthe water-soluble polymer is a partially-saponified polyvinyl alcohol.9. The composition according to claim 8, wherein thepartially-saponified polyvinyl alcohol has a degree of saponification of70% by mole or higher and 90% by mole or lower.
 10. A polishingcomposition comprising: a water-soluble polymer; an abrasive; and water,wherein the water-soluble polymer has a repeat unit A that has ahydroxyl group and a repeat unit B, the repeat unit B is at least oneselected from the group consisting of an acryloylmorpholine unit and anN-vinylpyrrolidone unit, the number of moles of the repeat unit B in thetotal number of moles of all the repeat units of the water-solublepolymer is 5% or greater, and the abrasive consists of silica particles.11. The composition according to claim 10, wherein the water-solublepolymer is nonionic.
 12. The composition according to claim 10, whereinthe number of moles of the repeat unit B in the total number of moles ofall the repeat units of the water-soluble polymer is 10% or greater. 13.The composition according to claim 10, wherein the water-soluble polymerhas a hydroxyl group content in a range of 4 mmol/g or higher and 21mmol/g or lower.
 14. The composition according to claim 10, wherein therepeat unit A comprises a vinyl alcohol unit.
 15. The compositionaccording to claim 10, wherein the water-soluble polymer has a weightaverage molecular weight of 1×10⁴ or higher.
 16. The compositionaccording to claim 10, wherein a pH is 9.0 or more and 12.0 or less. 17.The composition according to claim 10, wherein the water-soluble polymeris a partially-saponified polyvinyl alcohol.